ISEE Word Problems Question 275: Answer and Explanation
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Question: 275
9. The equation x = 
is true for what value(s) of x?
- A. –2
- B. 0
- C. all real numbers
- D. There are no values for x that would make the equation true.
Correct Answer: A
Explanation:
A
First, multiply both sides by (4 + x): x(4 + x) = –4. Distribute the x: 4x + x2 = –4. Add 4 to both sides and order the left side by leading exponent: x2 + 4x + 4 = 0. Factor the left side of the equation: (x + 2)(x + 2) = 0. Set x + 2 equal to 0 and subtract 2 from both sides: x = –2.
Test the answers. The value in choice (A) allows the equation to balance, so eliminate choices (B) and (D). Test any other number, and the equation will not balance. Eliminate choice (C).