16Hit1600
Advanced MathVery hardQuotient of a difference of fourth powers

Advanced Math practice question

For all values of x, the expression (x⁴ − 16)/(x² + 4) is equivalent to x² − k, where k is a constant. What is the value of k?

Answer: 4

x⁴ − 16 = (x² − 4)(x² + 4), so dividing by x² + 4 leaves x² − 4.

Common wrong answers

If you answered 2
2 takes the square root once too often.
If you answered 16
16 copies the constant in the numerator.
If you answered -4
−4 has the sign wrong.

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