9х^2-7(x+4)*(4-x)-(1-4x)^2=15

Question

9х^2-7(x+4)*(4-x)-(1-4x)^2=15

Answer 1

9x^2-7(x+4)(4-x)-(1-4x)^2=15
9x^2-7(x+4)(4-x)-(1-8x+16x^2)=15
9^2-28x+7x^2-112+28x-1+8x-16x^2-15=0
8x-128=0
8x=128
x=16