ISEE Word Problems Question 273: Answer and Explanation

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Question: 273

7. What is the value of (x + 4)(x – 5)?

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

Correct Answer: C

Explanation:

C

Use FOIL (First, Outside, Inside, Last) on the two factors: (x + 4)(x – 5) = (x2 + 4x– 5x – 20). Combine like terms: x2x – 20.

Plug in a number for x, such as x = 6, and solve: (6 + 4)(6 – 5) = (10)(1) = 10. Only choice (C) yields 10 when the value for x is plugged in.

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