Advanced Math practice question

Answer: 10

One real zero means the discriminant is zero: k² − 4(1)(25) = 0, so k² = 100 and k = 10 (taking the positive root). Then x² + 10x + 25 = (x + 5)².

Common wrong answers

If you answered 5

5 is the number inside the perfect square (x + 5)²; k is twice that.

If you answered 25

25 is the constant term, not k.

If you answered 100

100 is k², one step short of k.

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