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College Algebra Quiz

College Algebra Quiz: Radical Equations And Extraneous Solutions

Practice Radical Equations And Extraneous Solutions in College Algebra with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

Question 1 / 20

0 of 20 answered

Solve for xxx and check for extraneous solutions: x+4=9.\sqrt{x}+4=9.x​+4=9.

Select an answer to continue

What this quiz covers

This quiz focuses on Radical Equations And Extraneous Solutions, giving you a quick way to practice the rules, question types, and explanations that matter most for College Algebra.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

Solve for xxx and check for extraneous solutions: x+4=9.\sqrt{x}+4=9.x​+4=9.

  1. x=13x=13x=13, verified by substitution
  2. x=25x=25x=25, verified by substitution (correct answer)
  3. x=5x=5x=5, verified by substitution
  4. x=81x=81x=81, verified by substitution

Explanation: This question tests solving radical equations and identifying extraneous solutions. Radical equations often produce extraneous solutions when both sides are squared to eliminate the radical. In the given problem, isolating the radical is key; subtract 4 to get √x = 5, then square to find x = 25. The correct answer is choice B because it accurately reflects the solution process and checks for extraneous solutions by substitution. A common error is found in choice C, where students might subtract incorrectly, leading to x = 5 which doesn't satisfy. To teach this skill, emphasize the importance of verifying solutions by substitution and understanding domain restrictions. Encourage practice with a variety of radical equations to recognize potential pitfalls.

Question 2

Solve for xxx and check for extraneous solutions: x+2=5.\sqrt{x}+2=5.x​+2=5.

  1. x=3x=3x=3, verified by substitution
  2. x=7x=7x=7, verified by substitution
  3. x=9x=9x=9, verified by substitution (correct answer)
  4. x=25x=25x=25, verified by substitution

Explanation: This question tests solving radical equations and identifying extraneous solutions. Radical equations often produce extraneous solutions when both sides are squared to eliminate the radical. In the given problem, isolating the radical is key; subtract 2 to get √x = 3, then square to find x = 9. The correct answer is choice C because it accurately reflects the solution process and checks for extraneous solutions by substitution. A common error is found in choice D, where students might add instead of subtract, leading to x = 25 which doesn't satisfy. To teach this skill, emphasize the importance of verifying solutions by substitution and understanding domain restrictions. Encourage practice with a variety of radical equations to recognize potential pitfalls.

Question 3

Solve for xxx and check for extraneous solutions: x−4= 2.\sqrt{x-4}=\,2.x−4​=2.

  1. x=0x=0x=0, verified by substitution
  2. x=6x=6x=6, verified by substitution
  3. x=4x=4x=4, verified by substitution
  4. x=8x=8x=8, verified by substitution (correct answer)

Explanation: This question tests solving radical equations and identifying extraneous solutions. Radical equations often produce extraneous solutions when both sides are squared to eliminate the radical. In the given problem, isolating the radical is key; the radical is already isolated, so square to x - 4 = 4, then solve to x = 8. The correct answer is choice D because it accurately reflects the solution process and checks for extraneous solutions by substitution. A common error is found in choice A, where students might set x = 0 without solving properly, leading to an invalid solution. To teach this skill, emphasize the importance of verifying solutions by substitution and understanding domain restrictions. Encourage practice with a variety of radical equations to recognize potential pitfalls.

Question 4

Solve for xxx and check for extraneous solutions: x+5=2.\sqrt{x+5}=2.x+5​=2.

  1. x=−1x=-1x=−1, verified by substitution (correct answer)
  2. x=1x=1x=1, verified by substitution
  3. x=9x=9x=9, verified by substitution
  4. x=−9x=-9x=−9, verified by substitution

Explanation: This question tests solving radical equations and identifying extraneous solutions. Radical equations often produce extraneous solutions when both sides are squared to eliminate the radical. In the given problem, isolating the radical is key; the radical is already isolated, so square both sides to get x + 5 = 4, then solve to find x = -1. The correct answer is choice A because it accurately reflects the solution process and checks for extraneous solutions by substitution. A common error is found in choice B, where students might ignore the domain and reject negative solutions prematurely, but x = -1 works. To teach this skill, emphasize the importance of verifying solutions by substitution and understanding domain restrictions. Encourage practice with a variety of radical equations to recognize potential pitfalls.

Question 5

Solve for xxx and check for extraneous solutions: x+3=7.\sqrt{x}+3=7.x​+3=7.

  1. x=8x=8x=8, verified by substitution
  2. x=16x=16x=16, verified by substitution (correct answer)
  3. x=4x=4x=4, verified by substitution
  4. x=1x=1x=1, verified by substitution

Explanation: This question tests solving radical equations and identifying extraneous solutions. Radical equations often produce extraneous solutions when both sides are squared to eliminate the radical. In the given problem, isolating the radical is key; subtract 3 from both sides to get √x = 4, then square both sides and simplify to find x = 16. The correct answer is choice B because it accurately reflects the solution process and checks for extraneous solutions by substitution. A common error is found in choice A, where students might mistakenly subtract and square incorrectly, leading to accepting x = 8 which doesn't satisfy the original equation. To teach this skill, emphasize the importance of verifying solutions by substitution and understanding domain restrictions. Encourage practice with a variety of radical equations to recognize potential pitfalls.

Question 6

Solve for xxx and check for extraneous solutions: 2x+1=4.\sqrt{2x+1}=4.2x+1​=4.

  1. x=6.5x=6.5x=6.5, verified by substitution
  2. x=7.5x=7.5x=7.5, verified by substitution (correct answer)
  3. x=8.5x=8.5x=8.5, verified by substitution
  4. x=9.5x=9.5x=9.5, verified by substitution

Explanation: This question tests solving radical equations and identifying extraneous solutions. Radical equations often produce extraneous solutions when both sides are squared to eliminate the radical. In the given problem, isolating the radical is key; the radical is already isolated, so square to 2x + 1 = 16, then solve to x = 7.5. The correct answer is choice B because it accurately reflects the solution process and checks for extraneous solutions by substitution. A common error is found in choice A, where students might miscalculate the division, leading to x = 6.5 which doesn't satisfy. To teach this skill, emphasize the importance of verifying solutions by substitution and understanding domain restrictions. Encourage practice with a variety of radical equations to recognize potential pitfalls.

Question 7

Solve for xxx and check for extraneous solutions: 2x−1=7.\sqrt{2x-1}=7.2x−1​=7.

  1. x=24x=24x=24, verified by substitution
  2. x=25x=25x=25, verified by substitution (correct answer)
  3. x=49x=49x=49, verified by substitution
  4. x=23x=23x=23, verified by substitution

Explanation: This question tests solving radical equations and identifying extraneous solutions. Radical equations often produce extraneous solutions when both sides are squared to eliminate the radical. In the given problem, isolating the radical is key; the radical is already isolated, so square to 2x - 1 = 49, then solve to x = 25. The correct answer is choice B because it accurately reflects the solution process and checks for extraneous solutions by substitution. A common error is found in choice A, where students might forget to add back the 1, leading to x = 24 which doesn't satisfy. To teach this skill, emphasize the importance of verifying solutions by substitution and understanding domain restrictions. Encourage practice with a variety of radical equations to recognize potential pitfalls.

Question 8

Solve for xxx and check for extraneous solutions: 3x=6.\sqrt{3x}=6.3x​=6.

  1. x=12x=12x=12, verified by substitution (correct answer)
  2. x=9x=9x=9, verified by substitution
  3. x=18x=18x=18, verified by substitution
  4. x=6x=6x=6, verified by substitution

Explanation: This question tests solving radical equations and identifying extraneous solutions. Radical equations often produce extraneous solutions when both sides are squared to eliminate the radical. In the given problem, isolating the radical is key; the radical is √(3x) = 6, square to 3x = 36, then divide by 3 to x = 12. The correct answer is choice A because it accurately reflects the solution process and checks for extraneous solutions by substitution. A common error is found in choice D, where students might divide incorrectly, leading to x = 6 which doesn't satisfy. To teach this skill, emphasize the importance of verifying solutions by substitution and understanding domain restrictions. Encourage practice with a variety of radical equations to recognize potential pitfalls.

Question 9

Solve for xxx and check for extraneous solutions: 2x+5=11.2\sqrt{x}+5=11.2x​+5=11.

  1. x=9x=9x=9, verified by substitution (correct answer)
  2. x=36x=36x=36, verified by substitution
  3. x=3x=3x=3, verified by substitution
  4. x=18x=18x=18, verified by substitution

Explanation: This question tests solving radical equations and identifying extraneous solutions. Radical equations often produce extraneous solutions when both sides are squared to eliminate the radical. In the given problem, isolating the radical is key; subtract 5 to get 2√x = 6, divide by 2 to get √x = 3, then square to find x = 9. The correct answer is choice A because it accurately reflects the solution process and checks for extraneous solutions by substitution. A common error is found in choice B, where students fail to isolate properly and square the entire side, leading to accepting x = 36 which doesn't satisfy. To teach this skill, emphasize the importance of verifying solutions by substitution and understanding domain restrictions. Encourage practice with a variety of radical equations to recognize potential pitfalls.

Question 10

Solve for xxx and check for extraneous solutions: x+1=9.\sqrt{x}+1=\sqrt{9}.x​+1=9​.

  1. x=4x=4x=4, verified by substitution (correct answer)
  2. x=9x=9x=9, verified by substitution
  3. x=16x=16x=16, verified by substitution
  4. x=1x=1x=1, verified by substitution

Explanation: This question tests solving radical equations and identifying extraneous solutions. Radical equations often produce extraneous solutions when both sides are squared to eliminate the radical. In the given problem, isolating the radical is key; subtract 1 to get √x = √9 - 1 = 2, then square to find x = 4. The correct answer is choice A because it accurately reflects the solution process and checks for extraneous solutions by substitution. A common error is found in choice B, where students might square both sides without isolating, leading to complex equations and invalid x = 9. To teach this skill, emphasize the importance of verifying solutions by substitution and understanding domain restrictions. Encourage practice with a variety of radical equations to recognize potential pitfalls.

Question 11

Solve for xxx and check for extraneous solutions: x/4=3.\sqrt{x/4}=3.x/4​=3.

  1. x=12x=12x=12, verified by substitution
  2. x=9x=9x=9, verified by substitution
  3. x=36x=36x=36, verified by substitution (correct answer)
  4. x=4x=4x=4, verified by substitution

Explanation: This question tests solving radical equations and identifying extraneous solutions. Radical equations often produce extraneous solutions when both sides are squared to eliminate the radical. In the given problem, isolating the radical is key; the radical is √(x/4) = 3, square to x/4 = 9, then multiply by 4 to x = 36. The correct answer is choice C because it accurately reflects the solution process and checks for extraneous solutions by substitution. A common error is found in choice B, where students might multiply incorrectly, leading to x = 9 which doesn't satisfy. To teach this skill, emphasize the importance of verifying solutions by substitution and understanding domain restrictions. Encourage practice with a variety of radical equations to recognize potential pitfalls.

Question 12

Solve for xxx and check for extraneous solutions: 3x−4=11.3\sqrt{x}-4=11.3x​−4=11.

  1. x=9x=9x=9, verified by substitution
  2. x=25x=25x=25, verified by substitution (correct answer)
  3. x=3x=3x=3, verified by substitution
  4. x=49x=49x=49, verified by substitution

Explanation: This question tests solving radical equations and identifying extraneous solutions. Radical equations often produce extraneous solutions when both sides are squared to eliminate the radical. In the given problem, isolating the radical is key; add 4 to get 3√x = 15, divide by 3 to get √x = 5, then square to find x = 25. The correct answer is choice B because it accurately reflects the solution process and checks for extraneous solutions by substitution. A common error is found in choice A, where students might square without isolating fully, leading to x = 9 which doesn't satisfy. To teach this skill, emphasize the importance of verifying solutions by substitution and understanding domain restrictions. Encourage practice with a variety of radical equations to recognize potential pitfalls.

Question 13

Solve and check: 5x−5=10\sqrt{5x-5}=105x−5​=10 Which value of xxx is a valid solution?

  1. x=15x=15x=15
  2. x=19x=19x=19
  3. x=21x=21x=21 (correct answer)
  4. x=25x=25x=25

Explanation: This question tests solving radical equations and identifying extraneous solutions. Radical equations often produce extraneous solutions when both sides are squared to eliminate the radical. In the given problem, isolating the radical is key; solve by squaring both sides and simplifying the resulting equation. The correct answer is choice C because x=21 satisfies √(105-5) = √100 = 10. A common error is found in choice D, where students fail to check solutions back in the original equation, leading to accepting invalid solutions like x=25 which gives √(125-5) = √120 ≈ 10.95 ≠ 10. To teach this skill, emphasize the importance of verifying solutions by substitution and understanding domain restrictions. Encourage practice with a variety of radical equations to recognize potential pitfalls.

Question 14

Solve for xxx and check: 2x+5=112\sqrt{x}+5=112x​+5=11 Which solution is valid after substituting back to avoid extraneous results?

  1. x=9x=9x=9 (correct answer)
  2. x=3x=3x=3
  3. x=36x=36x=36
  4. x=1x=1x=1

Explanation: This question tests solving radical equations and identifying extraneous solutions. Radical equations often produce extraneous solutions when both sides are squared to eliminate the radical. In the given problem, isolating the radical is key; solve by squaring both sides and simplifying the resulting equation. The correct answer is choice A because x=9 satisfies 2√9 + 5 = 6 + 5 = 11 after verification. A common error is found in choice C, where students fail to check solutions back in the original equation, leading to accepting invalid solutions like x=36 which gives 2*6 + 5 = 17 ≠ 11. To teach this skill, emphasize the importance of verifying solutions by substitution and understanding domain restrictions. Encourage practice with a variety of radical equations to recognize potential pitfalls.

Question 15

Solve and check: x+1=9\sqrt{x}+1=\sqrt{9}x​+1=9​ Which value of xxx satisfies the original equation?

  1. x=4x=4x=4 (correct answer)
  2. x=8x=8x=8
  3. x=16x=16x=16
  4. x=9x=9x=9

Explanation: This question tests solving radical equations and identifying extraneous solutions. Radical equations often produce extraneous solutions when both sides are squared to eliminate the radical. In the given problem, isolating the radical is key; solve by squaring both sides and simplifying the resulting equation. The correct answer is choice A because x=4 satisfies √4 + 1 = 2 + 1 = 3 = √9. A common error is found in choice C, where students fail to check solutions back in the original equation, leading to accepting invalid solutions like x=16 which gives 4 + 1 = 5 ≠ 3. To teach this skill, emphasize the importance of verifying solutions by substitution and understanding domain restrictions. Encourage practice with a variety of radical equations to recognize potential pitfalls.

Question 16

Solve and check: x−1=4\sqrt{x-1}=4x−1​=4 Which value of xxx satisfies the original equation exactly?

  1. x=15x=15x=15
  2. x=17x=17x=17 (correct answer)
  3. x=8x=8x=8
  4. x=5x=5x=5

Explanation: This question tests solving radical equations and identifying extraneous solutions. Radical equations often produce extraneous solutions when both sides are squared to eliminate the radical. In the given problem, isolating the radical is key; solve by squaring both sides and simplifying the resulting equation. The correct answer is choice B because x=17 satisfies √(17-1) = √16 = 4 exactly. A common error is found in choice A, where students fail to check solutions back in the original equation, leading to accepting invalid solutions like x=15 which gives √14 ≈ 3.74 ≠ 4. To teach this skill, emphasize the importance of verifying solutions by substitution and understanding domain restrictions. Encourage practice with a variety of radical equations to recognize potential pitfalls.

Question 17

Which step verifies a solution to x+1=x−3\sqrt{x+1}=x-3x+1​=x−3 after solving the squared equation?

  1. Check by substituting into original equation (correct answer)
  2. Assume both squared solutions are valid
  3. Divide both sides by the radical
  4. Take square roots of both sides again

Explanation: This question tests solving radical equations and identifying extraneous solutions. Radical equations often produce extraneous solutions when both sides are squared to eliminate the radical. In the given problem, isolating the radical is key; solve by squaring both sides and simplifying the resulting equation. The correct answer is choice A because checking by substituting into the original equation verifies if it's valid or extraneous. A common error is found in choice B, where students fail to check solutions back in the original equation, leading to accepting invalid solutions without verification. To teach this skill, emphasize the importance of verifying solutions by substitution and understanding domain restrictions. Encourage practice with a variety of radical equations to recognize potential pitfalls.

Question 18

Solve and check: 2x−1+1=6\sqrt{2x-1}+1=62x−1​+1=6 Which value of xxx is a valid solution?

  1. x=18x=18x=18
  2. x=13x=13x=13 (correct answer)
  3. x=12.5x=12.5x=12.5
  4. x=9x=9x=9

Explanation: This question tests solving radical equations and identifying extraneous solutions. Radical equations often produce extraneous solutions when both sides are squared to eliminate the radical. In the given problem, isolating the radical is key; solve by squaring both sides and simplifying the resulting equation. The correct answer is choice B because x=13 satisfies √(26-1) + 1 = 5 + 1 = 6. A common error is found in choice A, where students fail to check solutions back in the original equation, leading to accepting invalid solutions like x=18 which gives √35 + 1 ≈ 6.92 ≠ 6. To teach this skill, emphasize the importance of verifying solutions by substitution and understanding domain restrictions. Encourage practice with a variety of radical equations to recognize potential pitfalls.

Question 19

Solve and check: 4x=6\sqrt{4x}=64x​=6 Which value of xxx satisfies the original equation?

  1. x=6x=6x=6
  2. x=9x=9x=9 (correct answer)
  3. x=12x=12x=12
  4. x=36x=36x=36

Explanation: This question tests solving radical equations and identifying extraneous solutions. Radical equations often produce extraneous solutions when both sides are squared to eliminate the radical. In the given problem, isolating the radical is key; solve by squaring both sides and simplifying the resulting equation. The correct answer is choice B because x=9 satisfies √(36) = 6. A common error is found in choice D, where students fail to check solutions back in the original equation, leading to accepting invalid solutions like x=36 which gives √144 = 12 ≠ 6. To teach this skill, emphasize the importance of verifying solutions by substitution and understanding domain restrictions. Encourage practice with a variety of radical equations to recognize potential pitfalls.

Question 20

The equation 3x−2=x−4\sqrt{3x - 2} = x - 43x−2​=x−4 has been solved by squaring both sides. Before accepting any solutions, what conditions must be verified?

  1. Only that 3x−2≥03x - 2 \geq 03x−2≥0 to ensure the radical is defined in real numbers
  2. Only that any solutions satisfy the original equation when substituted back
  3. Both that 3x−2≥03x - 2 \geq 03x−2≥0 and x−4≥0x - 4 \geq 0x−4≥0, plus verification in the original equation (correct answer)
  4. That 3x−2≥03x - 2 \geq 03x−2≥0, x−4≥0x - 4 \geq 0x−4≥0, and 3x−2=(x−4)23x - 2 = (x - 4)^23x−2=(x−4)2, without further checking

Explanation: When solving 3x−2=x−4\sqrt{3x - 2} = x - 43x−2​=x−4, we need multiple conditions: (1) 3x−2≥03x - 2 \geq 03x−2≥0 so the radical is defined, giving x≥23x \geq \frac{2}{3}x≥32​; (2) x−4≥0x - 4 \geq 0x−4≥0 because expression≥0\sqrt{\text{expression}} \geq 0expression​≥0 always, so if 3x−2=x−4\sqrt{3x - 2} = x - 43x−2​=x−4, then x−4≥0x - 4 \geq 0x−4≥0, giving x≥4x \geq 4x≥4; (3) Any solutions from squaring must be checked in the original equation since squaring can introduce extraneous solutions. The combined domain restriction is x≥4x \geq 4x≥4. Squaring gives 3x−2=x2−8x+163x - 2 = x^2 - 8x + 163x−2=x2−8x+16, so x2−11x+18=0x^2 - 11x + 18 = 0x2−11x+18=0, which factors as (x−2)(x−9)=0(x - 2)(x - 9) = 0(x−2)(x−9)=0. This gives x=2x = 2x=2 and x=9x = 9x=9. Since x=2<4x = 2 < 4x=2<4, it's rejected. Checking x=9x = 9x=9: 25=5\sqrt{25} = 525​=5 and 9−4=59 - 4 = 59−4=5 ✓.