Advanced Math practice question

Answer: -1 or −1

Substitute y = x + 1: x² + (x + 1)² = 25, so 2x² + 2x + 1 = 25, 2x² + 2x − 24 = 0, x² + x − 12 = 0, (x + 4)(x − 3) = 0. The x-values are −4 and 3, and their sum is −1.

Common wrong answers

If you answered 1

1 has the wrong sign: (x + 4)(x − 3) = 0 gives x = −4 and x = 3, which sum to −1.

If you answered 3

3 is only one of the two x-values; the other is −4.

If you answered -12

−12 is the PRODUCT of the x-values (−4 × 3), not the sum.

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