SAT Math Multiple Choice Question 932: Answer and Explanation

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Question: 932

16. If r < 0 and (4r – 4)2 = 36, what is the value of r?

  • A. –6
  • B. –2
  • C. –2
  • D.

Correct Answer: D



Difficulty: Medium

Category: Passport to Advanced Math / Quadratics

Strategic Advice: When both sides of a quadratic equation are perfect squares, use square rooting to solve for the variable. Just remember that you'll end up with two possible solutions (and you'll need to review the question to see which is correct).

Getting to the Answer: Take the square root of both sides of the equation to remove the exponent and get. You're looking for a value of r that is less than 0, so start by solving the equation with -6:

The value of r is indeed negative, so no need to try +6. Choice (D) is the correct answer. (Don't fall for choice A: 4r - 4 = -6, but you're looking for the value of r, not 4r - 4.)

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