SAT Math Multiple Choice Question 236: Answer and Explanation

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Question: 236

11. y = x2 - 2x
y = 2x - 1

This system has two solutions for (x, y). What is the larger value of x ?

  • A. 2-
  • B.
  • C. 2 +
  • D. 5

Correct Answer: C

Explanation:

C Start by setting the two equations equal to each other to get x2 - 2x = 2x - 1. Manipulate the equation into the ax2 + bx + c = 0 form, which is x2 - 4x + 1 = 0. Use the quadratic equation, which states that x = to get x = . Solve for x to get x = , then x = or x = , so x = 2 ±. The greater of the two possible values for x is x = 2 + . Therefore, the correct answer is (C).

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