Advanced MathHardConstant after simplifying a rational expression with a common factor
Advanced Math practice question
For x ≠ −2, (5x² − 20)/(5x + 10) is equivalent to x − k, where k is a constant. What is the value of k?
Answer: 2
5x² − 20 = 5(x − 2)(x + 2) and 5x + 10 = 5(x + 2). Cancel 5(x + 2): x − 2, so k = 2.
Common wrong answers
- If you answered 4
- 4 is 20/5 without factoring the difference of squares.
- If you answered 20
- 20 is the original constant.
- If you answered -2
- −2 would give x + 2, the cancelled factor.
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