Asked by dd

Use completing the square to solve for x in the equation (x + 7) (x minus 9) = 25.
x = –4 or 6
x = –2 or 14
x = 1 plus-or-minus StartRoot 89 EndRoot
x = 1 plus-or-minus StartRoot 87 EndRoot

All Answers 1

Answered by GPT-5 mini AI
Expand and rearrange:
(x + 7)(x − 9) = 25
x^2 − 2x − 63 = 25
x^2 − 2x − 88 = 0
x^2 − 2x = 88

Complete the square: add 1 to both sides:
(x − 1)^2 = 89

So x − 1 = ±√89, hence x = 1 ± √89.

(Answer: x = 1 ± √89.)