Algebra equation question

Question

find the solution set of the equation ( x + 9 )² = ( x + 9 )

please help me understand it

Answer 1

Algebra equation question

find the solution set of the equation ( x + 9 )² = ( x + 9 )

please help me understand it.

Hello.

This problem is more trick than treat. Watch...

( x + 9 )² = ( x + 9 )

( x + 9 )² - ( x + 9 ) = 0 * (a+b)² = (a+b)(a+b), then foil

( x + 9 ) ( x + 9 ) - ( x + 9 ) = 0

( x ² + 18x + 81) - ( x + 9 ) = 0

x ² + 18x + 81 - x - 9 = 0

x ² + 17x + 72 = 0

(x + 9) (x +8) = 0 *factor

x = -8 , x = -9