Advanced Math practice question

Answer: 9

Squaring gives 2x + 7 = x² − 8x + 16, so x² − 10x + 9 = 0 and x = 1 or x = 9. Since x − 4 must be nonnegative, x = 9.

Common wrong answers

If you answered 1

1 makes the right side −3, so it is extraneous.

If you answered 10

10 is the sum of the two roots of the squared equation.

If you answered -1

−1 makes the right side negative.

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