Equivalent Expressions

Help Questions

ACT Math › Equivalent Expressions

Questions 1 - 10
1

Simplify: $8 - (2x - 3)$

$2x + 11$

$11 - 2x$

$5 - 2x$

$8 - 2x + 3$

Explanation

Distribute the negative sign to both terms in the parentheses: 8 - (2x - 3) = 8 - 2x + 3. Combine the constant terms: 8 + 3 = 11, giving 8 - 2x + 3 = 11 - 2x. The simplified form is 11 - 2x, which equals -2x + 11.

2

Which of the following expressions is equivalent to $3(x - 4) + 2x$?

$x - 12$

$5x - 4$

$5x - 12$

$6x - 12$

Explanation

The correct answer is B (5x − 12). Distribute the 3 across the parentheses: 3(x − 4) = 3x − 12. Then combine like terms with 2x: 3x − 12 + 2x = 5x − 12. A (5x − 4) results from distributing 3 to x but not to −4, keeping −4 instead of computing 3 × (−4) = −12. C (6x − 12) comes from incorrectly treating the 2x as adding to the coefficient 3 rather than to 3x. D (x − 12) results from subtracting 2x rather than adding it. Distribution errors are extremely common — always multiply the outside factor by every term inside the parentheses.

3

For all $x$ and $y$, which of the following expressions is equivalent to $(3x^3y^2)(4xy^4)$?

$12x^3y^8$

$12x^4y^6$

$7x^4y^6$

$7x^3y^6$

Explanation

The correct answer is C (12x⁴y⁶). Multiply the coefficients: 3 × 4 = 12. Apply the product rule for exponents (add exponents of like bases): x³ × x¹ = x^(3+1) = x⁴; y² × y⁴ = y^(2+4) = y⁶. Result: 12x⁴y⁶. A (7x³y⁶) adds coefficients (3+4=7) instead of multiplying and doesn't add the x exponent. B (12x³y⁸) correctly multiplies coefficients but treats x³ as fixed and incorrectly adds the y exponents (possibly counting y⁴ twice). D (7x⁴y⁶) adds coefficients but correctly adds the exponents. Key rule: multiply coefficients, add exponents of like bases.

4

Which expression is equivalent to $(x + 2)(x - 2)$?

$x^2 - 2$

$x^2 - 4$

$x^2 + 4$

$2x^2 - 4$

Explanation

This is a difference of squares pattern: (a + b)(a - b) = a² - b². Apply this with a = x and b = 2: (x + 2)(x - 2) = x² - 2² = x² - 4. The middle terms cancel when expanding: x² - 2x + 2x - 4 = x² - 4. Choice B incorrectly shows +4 instead of -4.

5

Which expression is equivalent to $3x(2 + 5)$?

$21$

$7x$

$6x + 15x$

$21x$

Explanation

To simplify this expression, we need to first simplify inside the parentheses, then apply the distributive property. Inside the parentheses: 2 + 5 = 7. The expression becomes 3x(7) = 21x. We can also think of this as distributing: 3x(2 + 5) = 3x(2) + 3x(5) = 6x + 15x = 21x. Choice A incorrectly leaves the expression in distributed form without combining like terms.

6

Which of the following matches the expansion of $-3(2x - 5)$?

$-6x - 15$

$6x - 15$

$6x + 15$

$-6x + 15$

Explanation

Apply the distributive property with -3 multiplied by each term inside the parentheses. -3 × 2x = -6x and -3 × (-5) = +15 (negative times negative equals positive). Therefore, -3(2x - 5) = -6x + 15. Choice A incorrectly shows -15 instead of +15.

7

Which of the following expressions is equivalent to $4(a + 2b) - 2(a - 3b)$?

$2a + 5b$

$2a + 2b$

$2a + 14b$

$6a + 14b$

Explanation

This is a distribution and simplification question testing the distributive property with negatives. Choice D (2a + 14b) is correct — distribute the 4: 4a + 8b. Distribute the −2 across (a − 3b): −2a + 6b. Note: −2 × (−3b) = +6b, not −6b. Combine like terms: (4a − 2a) + (8b + 6b) = 2a + 14b. Choice A (2a + 2b) results from treating the second distribution as −2(a − 3b) = −2a − 6b (wrong sign on 3b), giving 8b − 6b = 2b. Choice B (2a + 5b) is an arithmetic error in combining the b terms, possibly computing 8b − 3b. Choice C (6a + 14b) adds 4a + 2a = 6a instead of subtracting, getting the sign wrong on the a-coefficient of the second term. Pro tip: When distributing a negative number, BOTH terms inside the parentheses change sign. Write out −2(a − 3b) = −2a + 6b before combining anything.

8

What is the simplified form of $7x - 3(2x - 4)$?

$x - 12$

$7x - 6x + 12$

$x + 12$

$13x - 12$

Explanation

To simplify this expression, we need to apply the distributive property. First, distribute the -3 to both terms in the parentheses: -3(2x - 4) = -6x + 12. The expression becomes 7x - 6x + 12. Combining like terms: (7x - 6x) + 12 = x + 12. Choice C incorrectly adds the coefficients of x terms instead of subtracting.

9

Which expression is equivalent to $x(x - 7) + 3x$?

$x^2 - 10x$

$x^2 - 7$

$x^2 + 4x$

$x^2 - 4x$

Explanation

First distribute x through the parentheses: x(x - 7) = x² - 7x. Then add 3x to get: x² - 7x + 3x = x² - 4x. Combine like terms: -7x + 3x = -4x, while the x² term remains unchanged. Choice B incorrectly shows -10x instead of -4x.

10

Which expression is equivalent to $2x^2(3x)$?

$6x^5$

$6x^6$

$5x^2$

$6x^3$

Explanation

Multiply the coefficients and add the exponents when multiplying powers with the same base. 2x² × 3x = (2 × 3)(x² × x) = 6x³. The exponents add: x² × x¹ = x²⁺¹ = x³. Choice A incorrectly multiplies the exponents instead of adding them.

Page 1 of 7