Answer
The solutions are -3 and 12.
Work Step by Step
(x+4)(x-9)=4x
$x^{2}$-9x+4x-36=4x
$x^{2}$-5x-36=4x
$x^{2}$-5x-36-4x=4x-4x
$x^{2}$-5x-36-4x=0
$x^{2}$-9x-36=0
$x^{2}$+3x-12x-36=0
x(x+3)-12(x+3)=0
(x-12)(x+3)=0
x+3=0 x-12=0
x+3-3=0-3 or x-12+12=0+12
x=-3 or x=12
The solutions are -3 and 12.
Check
Let x=-3
(x+4)(x-9)=4x
(-3+4)(-3-9)=4(-3)
1(-12)=-12
-12=-12
Let x=12
(x+4)(x-9)=4x
(12+4)(12-9)=4*12
16*3=48
48=48
