Use completing the square to solve (x + 7)(x – 9) = 25 for x.
x = –4 or 6
x = –2 or 14
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We need to solve for x by completing the square of the given mathematical expression (x+7)(x-9) = 25.
First, we need to perform multiplication of (x+7) and (x-9) such as the expression become:
(x+7) (x-9) = 25
x² -9x +7x -63 = 25
x² - 2x = 25 + 63
Then perform addition of constant values 25 and 63
x² - 2x =88
Add +1 in both sides to complete the expression such as:
x² - 2x +1 = 88 +1
(x-1)(x-1) = 89
(x-1)² = 89
We see that (x-1) is a perfect square, we can now solve for the value of x such as:
(x-1) = +-√89
x1 = +√89  + 1
x1 = 10.4
x2 = -√89 +1
x2 = -8.4

The answers are 10.4 and -8.4.