ISEE Word Problems Question 238: Answer and Explanation

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Question: 238

2. Which expression is equivalent to the expression (x – 4)(x + 5)?

  • A. x2 – 20
  • B. x2 + 1
  • C. x2x – 20
  • D. x2 + x – 20

Correct Answer: D

Explanation:

The answer is D

Use FOIL (First, Outside, Inside, Last) on the two factors: (x - 4)(x + 5) = (x2 + 5x - 4x - 20). Combine like terms: x2 + x - 20.

Plug in a number for x, such as x = 5, and solve: (5 - 4)(5 + 5) = (1)(10) = 10. Only choice (D) yields 10 when the value for x is plugged in.

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