Advanced Math practice question

Answer: 5

Square: 3x + 1 = x² − 2x + 1, so x² − 5x = x(x − 5) = 0, x = 0 or 5. Check x = 0: √1 = 1 but 0 − 1 = −1, rejected. Check x = 5: √16 = 4 = 5 − 1 ✓.

Common wrong answers

If you answered 0

0 is the extraneous root: it makes the right side −1, but a square root can't be negative.

If you answered 1

1 makes the left side 2 and the right side 0.

If you answered 4

4 makes the left side √13 and the right side 3.

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