Solving Rational and Radical Equations
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Algebra › Solving Rational and Radical Equations
Solve and check for extraneous solutions:
$$\frac{3}{x-2}=2$$
$x=\frac{7}{2}$
$x=1$
No solution (extraneous)
$x=\frac{1}{2}$
Explanation
This question tests your ability to solve rational equations and identify extraneous solutions—solutions that emerge from the solving process but don't actually satisfy the original equation. When solving rational equations (equations with variables in denominators), we multiply both sides by the LCD to clear all the fractions, which gives us a polynomial equation to solve. However, this multiplication can introduce extraneous solutions: if the LCD contains a factor like (x - 2) and our solution is x = 2, it's extraneous because it makes the original denominators zero (undefined!). Always check that solutions don't make any denominator in the original equation equal zero. Solving $\frac{3}{x-2}=2$: (1) Multiply both sides by (x-2): $3 = 2(x-2)$. (2) Distribute: $3 = 2x - 4$. (3) Solve: $7 = 2x$, so $x = \frac{7}{2}$. (4) Check in original: Does $x = \frac{7}{2}$ make the denominator zero? $\frac{7}{2} - 2 = \frac{3}{2} \neq 0$. Good! Verify it satisfies equation: $\frac{3}{\frac{3}{2}} = \frac{3 \cdot 2}{3} = 2$. ✓ Final answer: $x = \frac{7}{2}$. Choice C correctly solves to get $x = \frac{7}{2}$ and verifies it doesn't make the denominator zero, confirming it's a valid solution. Choice A gives $x = 1$, which would make the left side $\frac{3}{1-2} = \frac{3}{-1} = -3$, not 2. This is an arithmetic error—always double-check your algebra! The rational equation solving recipe: (1) Find the LCD of all denominators, (2) Multiply EVERY term (both sides, all terms) by the LCD—fractions will cancel, (3) Solve the resulting polynomial equation, (4) Check each solution: does it make any original denominator equal zero? If yes, it's extraneous—reject it! If no, verify it satisfies the original equation. Keep only valid solutions. The checking step is non-negotiable!
Solve and check for extraneous solutions: $$\sqrt{x+3}=x-3.$$
${1}$ only (and $x=6$ is extraneous)
${6}$ only (and $x=1$ is extraneous)
${1,6}$ (both valid)
$\varnothing$
Explanation
This question tests your ability to solve radical equations and identify extraneous solutions—solutions that emerge from the solving process but don't actually satisfy the original equation. When solving radical equations (equations with variables under radicals like $ \sqrt{x + 3} = 5 $), we isolate the radical and then square both sides to eliminate the radical, giving a polynomial equation. But squaring can introduce extraneous solutions: if the original has $ \sqrt{(\dots)} = \text{negative} $, there's no real solution, but squaring gives a positive equation that might have solutions. Always substitute back into the ORIGINAL equation to verify—if it doesn't work, it's extraneous! Solving $ \sqrt{x+3} = x-3 $: (1) Isolate radical (already). (2) Square both sides: $ x+3 = (x-3)^2 $ → $ x+3 = x^2-6x+9 $. (3) Solve: $ x^2-7x+6=0 $ → $ (x-1)(x-6)=0 $, $ x=1 $ or $ 6 $. (4) Check each in ORIGINAL: For $ x=1 $: $ \sqrt{4}=2 $, $ 1-3=-2 $, $ 2≠-2 $, extraneous. For $ x=6 $: $ \sqrt{9}=3 $, $ 6-3=3 $, matches. Valid solution $ x=6 $, extraneous $ x=1 $. Choice B correctly solves to get $ {6} $ only and rejects $ x=1 $ as extraneous because it produces a negative on the right while left is positive, with proper checking. Choice A $ {1,6} $ includes $ x=1 $ as a valid solution, but checking: $ \sqrt{1+3}=2 ≠1-3=-2 $, doesn't satisfy original. This is extraneous! Always verify: for radical, does substituting back work? If it fails, reject the solution. For radical equations: (1) Isolate the radical on one side if possible (makes squaring cleaner), (2) Square both sides (if square root), (3) Solve the resulting equation (might be quadratic!), (4) Check EVERY solution in the ORIGINAL equation—substitute and see if both sides match. If a solution makes the radical expression negative or doesn't satisfy the equation, it's extraneous. Some radical equations have no valid solutions—all turned out extraneous!
Solve and check for extraneous solutions:
$$\frac{x}{x-2}=3$$
$x=-3$
$x=2$
$x=3$
No solution (the only solution makes the denominator zero)
Explanation
This question tests your ability to solve rational equations and identify extraneous solutions—solutions that emerge from the solving process but don't actually satisfy the original equation. When solving rational equations (equations with variables in denominators), we multiply both sides by the LCD to clear all the fractions, which gives us a polynomial equation to solve. However, this multiplication can introduce extraneous solutions: if the LCD contains a factor like (x - 3) and our solution is $x=3$, it's extraneous because it makes the original denominators zero (undefined!). Always check that solutions don't make any denominator in the original equation equal zero. Solving the rational equation $x/(x-2)=3$: (1) Identify the LCD: x-2. (2) Multiply every term by the LCD: $x=3(x-2)$. (3) Simplify: $x=3x-6 \rightarrow -2x=-6 \rightarrow x=3$. (4) Check in original: Does $x=3$ make denominator zero? $3-2=1 \neq 0$. Verify it satisfies: $3/1=3$, yes—valid! Final answer: $x=3$. Choice A correctly solves to get $x=3$ and confirms it's valid with proper checking, as it doesn't make the denominator zero and satisfies the equation. Choice D states no solution (the only solution makes the denominator zero), but while $x=2$ would be extraneous (makes denominator zero), our solution $x=3$ is valid—don't assume the root of the denominator is always the solution. The rational equation solving recipe: (1) Find the LCD of all denominators, (2) Multiply EVERY term (both sides, all terms) by the LCD—fractions will cancel, (3) Solve the resulting polynomial equation, (4) Check each solution: does it make any original denominator equal zero? If yes, it's extraneous—reject it! If no, verify it satisfies the original equation. Keep only valid solutions. The checking step is non-negotiable!
Solve and check for extraneous solutions: $$\sqrt{x+5}+1=x.$$
${4}$
No real solution
${5}$
${4,0}$
Explanation
This question tests your ability to solve radical equations and identify extraneous solutions—solutions that emerge from the solving process but don't actually satisfy the original equation. When solving radical equations (equations with variables under radicals like √(x + 3) = 5), we isolate the radical and then square both sides to eliminate the radical, giving a polynomial equation. But squaring can introduce extraneous solutions: if the original has √(...) = negative, there's no real solution, but squaring gives a positive equation that might have solutions. Always substitute back into the ORIGINAL equation to verify—if it doesn't work, it's extraneous! Solving $\sqrt{x+5}$+1=x: (1) Isolate radical: √(x+5)=x-1. (2) Square both sides: x+5 = $(x-1)^2$ → x+5 = $x^2$-2x+1. (3) Solve: $x^2$-3x-4=0 → (x-4)(x+1)=0, x=4 or x=-1. (4) Check each in ORIGINAL: For x=4: √(4+5)+1=√9+1=3+1=4, matches x=4, valid. For x=-1: √(-1+5)+1=√4+1=2+1=3 ≠ x=-1, extraneous. Conclusion: Valid solution is 4, extraneous is -1. Choice A correctly identifies {4} as the solution set with proper checking. Choice D says no real solution, but we found a valid one; perhaps from rejecting both without checking, but x=4 works—always verify by substitution! For radical equations: (1) Isolate the radical on one side if possible (makes squaring cleaner), (2) Square both sides (if square root) or cube (if cube root), (3) Solve the resulting equation (might be quadratic!), (4) Check EVERY solution in the ORIGINAL equation—substitute and see if both sides match. If a solution makes the radical expression negative or doesn't satisfy the equation, it's extraneous. Some radical equations have no valid solutions—all turned out extraneous!
Solve and check for extraneous solutions:
$$\frac{x}{x-5}=3$$
No solution (extraneous)
$x=\frac{15}{2}$
$x=\frac{5}{2}$
$x=5$ (valid)
Explanation
This question tests your ability to solve rational equations and identify extraneous solutions—solutions that emerge from the solving process but don't actually satisfy the original equation. When solving rational equations (equations with variables in denominators), we multiply both sides by the LCD to clear all the fractions, which gives us a polynomial equation to solve. However, this multiplication can introduce extraneous solutions: if the LCD contains a factor like $(x - 3)$ and our solution is $x = 3$, it's extraneous because it makes the original denominators zero (undefined!). Always check that solutions don't make any denominator in the original equation equal zero. Solving $$\frac{x}{x-5} = 3$$: (1) The LCD is $(x-5)$. (2) Multiply both sides by $(x-5)$: $x = 3(x-5)$. (3) Simplify: $x = 3x - 15$. (4) Solve: $x - 3x = -15 \to -2x = -15 \to x = \frac{15}{2}$. (5) Check in original: Does $x = \frac{15}{2}$ make the denominator zero? $x - 5 = \frac{15}{2} - 5 = \frac{15}{2} - \frac{10}{2} = \frac{5}{2} \neq 0$. Good! Now verify it satisfies the equation: $$\frac{\frac{15}{2}}{5/2} = \frac{15}{2} \times \frac{2}{5} = \frac{15}{5} = 3$$ ✓. Final answer: $x = \frac{15}{2}$. Choice A correctly solves to get $x = \frac{15}{2}$ and this value doesn't make the denominator zero, so it's valid. Choice B suggests $x = 5$ is valid, but this would make the denominator $x - 5 = 5 - 5 = 0$, causing division by zero in the original equation. This is the classic extraneous solution for rational equations! Always verify: For rational equations, does the solution make any denominator zero? If yes, it's extraneous and must be rejected. The rational equation solving recipe: (1) Find the LCD of all denominators, (2) Multiply EVERY term (both sides, all terms) by the LCD—fractions will cancel, (3) Solve the resulting polynomial equation, (4) Check each solution: does it make any original denominator equal zero? If yes, it's extraneous—reject it! If no, verify it satisfies the original equation. Keep only valid solutions. The checking step is non-negotiable!
Solve and check for extraneous solutions: $$\sqrt{x} = 2 - x.$$
${1,4}$ (both valid)
${1}$ only (and $x=4$ is extraneous)
${4}$ only (and $x=1$ is extraneous)
$\varnothing$
Explanation
This question tests your ability to solve radical equations and identify extraneous solutions—solutions that emerge from the solving process but don't actually satisfy the original equation. When solving radical equations (equations with variables under radicals like $\sqrt{x + 3} = 5$), we isolate the radical and then square both sides to eliminate the radical, giving a polynomial equation. But squaring can introduce extraneous solutions: if the original has $\sqrt{...} = \text{negative}$, there's no real solution, but squaring gives a positive equation that might have solutions. Always substitute back into the ORIGINAL equation to verify—if it doesn't work, it's extraneous! Solving $\sqrt{x} = 2 - x$: (1) Isolate radical (already). (2) Square both sides: $x = (2 - x)^2 \to x = 4 - 4x + x^2$. (3) Solve: $x^2 - 5x + 4 = 0 \to(x - 1)(x - 4) = 0$, $x = 1$ or $4$. (4) Check each in ORIGINAL: For $x=1$: $\sqrt{1} = 1$, $2 - 1 = 1$, matches. For $x=4$: $\sqrt{4} = 2$, $2 - 4 = -2$, $2 \neq -2$, extraneous. Valid $x=1$, extraneous $x=4$. Choice A correctly identifies ${1}$ only and rejects $x=4$ as extraneous because it produces negative on right while left positive, with proper checking. Choice C ${1,4}$ includes $x=4$ as a valid solution, but checking: $\sqrt{4} = 2 \neq 2 - 4 = -2$, doesn't satisfy original. This is extraneous! Always verify: for radical, does substituting back work? If it fails, reject the solution. For radical equations: (1) Isolate the radical on one side if possible (makes squaring cleaner), (2) Square both sides (if square root), (3) Solve the resulting equation (might be quadratic!), (4) Check EVERY solution in the ORIGINAL equation—substitute and see if both sides match. If a solution makes the radical expression negative or doesn't satisfy the equation, it's extraneous. Some radical equations have no valid solutions—all turned out extraneous!
Solve and check for extraneous solutions:
$$\frac{x}{x-3}=2$$
${6}$
${0}$
${3}$
${-6}$
Explanation
This question tests your ability to solve rational equations and identify extraneous solutions—solutions that emerge from the solving process but don't actually satisfy the original equation. When solving rational equations (equations with variables in denominators), we multiply both sides by the LCD to clear all the fractions, which gives us a polynomial equation to solve. However, this multiplication can introduce extraneous solutions: if the LCD contains a factor like (x - 3) and our solution is x = 3, it's extraneous because it makes the original denominators zero (undefined!). Always check that solutions don't make any denominator in the original equation equal zero. Solving $\frac{x}{x-3}=2$: (1) The denominator is (x-3), so multiply both sides by (x-3): $x = 2(x-3)$. (2) Simplify: $x = 2x - 6$. (3) Solve: $x - 2x = -6$, so $-x = -6$, thus $x = 6$. (4) Check in original: Does x = 6 make the denominator zero? $6 - 3 = 3 ≠ 0$, so it's valid! Verify it satisfies the equation: $\frac{6}{6-3} = \frac{6}{3} = 2$ ✓. Final answer: {6}. Choice A correctly solves to get x = 6 and verifies it doesn't make the denominator zero, confirming it as the valid solution. Choice B might result from an arithmetic error when solving -x = -6, incorrectly getting x = 3, but x = 3 would make the denominator (x-3) = 0, creating division by zero—definitely extraneous! The rational equation solving recipe: (1) Find the LCD of all denominators, (2) Multiply EVERY term (both sides, all terms) by the LCD—fractions will cancel, (3) Solve the resulting polynomial equation, (4) Check each solution: does it make any original denominator equal zero? If yes, it's extraneous—reject it! If no, verify it satisfies the original equation. Keep only valid solutions. The checking step is non-negotiable!
What is the solution set (excluding extraneous) for $$\frac{x+1}{x-1}=2?$$
${3}$
${0}$
${1}$
${3,1}$
Explanation
This question tests your ability to solve rational equations and identify extraneous solutions—solutions that emerge from the solving process but don't actually satisfy the original equation. When solving rational equations (equations with variables in denominators), we multiply both sides by the LCD to clear all the fractions, which gives us a polynomial equation to solve. However, this multiplication can introduce extraneous solutions: if the LCD contains a factor like (x - 3) and our solution is x = 3, it's extraneous because it makes the original denominators zero (undefined!). Always check that solutions don't make any denominator in the original equation equal zero. Solving $\frac{x+1}{x-1}$=2: (1) Identify the LCD: x-1. (2) Multiply every term by the LCD: x+1 = 2(x-1). (3) Simplify (fractions clear out): x+1 = 2x-2. (4) Solve: 3=x. (5) Check in original: Does x=3 make any denominator zero? 3-1=2 ≠0. Verify it satisfies equation: (3+1)/(3-1)=4/2=2. Final answer: {3}. Choice A correctly identifies {3} as the solution set with proper checking. Choice D includes x=3 and x=1 as valid solutions, but checking: x=1 makes denominator 1-1=0, undefined. This is extraneous! Always verify: (1) For rational, does it make any denominator zero? (2) For radical, does substituting back work? If either fails, reject the solution. The rational equation solving recipe: (1) Find the LCD of all denominators, (2) Multiply EVERY term (both sides, all terms) by the LCD—fractions will cancel, (3) Solve the resulting polynomial equation, (4) Check each solution: does it make any original denominator equal zero? If yes, it's extraneous—reject it! If no, verify it satisfies the original equation. Keep only valid solutions. The checking step is non-negotiable!
A student solved the radical equation below by squaring both sides and got $x=1$ and $x=6$.
$$\sqrt{x+3}=x-3$$
Which statement correctly identifies the valid solution(s)?
Both $x=1$ and $x=6$ are valid
Only $x=1$ is valid; $x=6$ is extraneous
Neither is valid; both are extraneous
Only $x=6$ is valid; $x=1$ is extraneous
Explanation
This question tests your ability to solve radical equations and identify extraneous solutions—solutions that emerge from the solving process but don't actually satisfy the original equation. When solving radical equations (equations with variables under radicals like $\sqrt{x + 3} = 5$), we isolate the radical and then square both sides to eliminate the radical, giving a polynomial equation. But squaring can introduce extraneous solutions: if the original has $\sqrt{...} =$ negative, there's no real solution, but squaring gives a positive equation that might have solutions. Always substitute back into the ORIGINAL equation to verify—if it doesn't work, it's extraneous! Testing the proposed solutions in the original equation $\sqrt{x+3}=x-3$: For $x=1$: $\sqrt{1+3}=\sqrt{4}=2$, right side $1-3=-2$, $2 \neq -2$, extraneous because left positive $\neq$ right negative. For $x=6$: $\sqrt{6+3}=\sqrt{9}=3$, right side $6-3=3$, $3=3$, valid because both sides equal. Therefore, only $x=6$ is valid, $x=1$ is extraneous. Choice C correctly rejects $x=1$ as extraneous because it doesn't satisfy the original equation (produces opposite signs) with proper checking. Choice B rejects a valid solution: $x=6$ actually DOES satisfy the original equation when we check: $\sqrt{6+3}=3=6-3$. Just because a solution looks unusual or emerged from squaring doesn't automatically make it extraneous—you must verify by substitution. This one checks out! For radical equations: (1) Isolate the radical on one side if possible (makes squaring cleaner), (2) Square both sides (if square root) or cube (if cube root), (3) Solve the resulting equation (might be quadratic!), (4) Check EVERY solution in the ORIGINAL equation—substitute and see if both sides match. If a solution makes the radical expression negative or doesn't satisfy the equation, it's extraneous. Some radical equations have no valid solutions—all turned out extraneous!
Solve and check for extraneous solutions: $$\frac{3}{x-1}+2=5.$$
${2}$
${2,1}$
${4}$
${1}$
Explanation
This question tests your ability to solve rational equations and identify extraneous solutions—solutions that emerge from the solving process but don't actually satisfy the original equation. When solving rational equations (equations with variables in denominators), we multiply both sides by the LCD to clear all the fractions, which gives us a polynomial equation to solve. However, this multiplication can introduce extraneous solutions: if the LCD contains a factor like $(x - 3)$ and our solution is $x = 3$, it's extraneous because it makes the original denominators zero (undefined!). Always check that solutions don't make any denominator in the original equation equal zero. Solving $3/(x-1) + 2 = 5$: (1) First, isolate the fraction: $3/(x-1) = 5 - 2 = 3$. (2) Now we have $3/(x-1) = 3$. (3) Cross multiply: $3 = 3(x-1)$. (4) Simplify: $3 = 3x - 3$. (5) Solve: $6 = 3x \rightarrow x = 2$. (6) Check in original: Does $x = 2$ make any denominator zero? The only denominator is $(x-1)$, and $2-1 = 1 \neq 0$. Good! Verify it satisfies equation: $3/(2-1) + 2 = 3/1 + 2 = 3 + 2 = 5 \checkmark$. Final answer: $x = 2$. Choice A correctly solves to get $x = 2$ with proper checking. Choice B would give $x = 1$, but checking: this makes the denominator $(x-1) = (1-1) = 0$, which is undefined! This would be extraneous if it appeared as a solution. Always verify: for rational equations, does the solution make any denominator zero? If yes, reject it as extraneous. The rational equation solving recipe: (1) Find the LCD of all denominators, (2) Multiply EVERY term (both sides, all terms) by the LCD—fractions will cancel, (3) Solve the resulting polynomial equation, (4) Check each solution: does it make any original denominator equal zero? If yes, it's extraneous—reject it! If no, verify it satisfies the original equation. Keep only valid solutions. The checking step is non-negotiable!