Question

(5(x+5)^2)+(2(x+5)^2)-7=0

Answer 1

it's easier to see what you have if you let

u = x+5

Then you have

5u^2+2u-7=0
(5u+7)(u-1) = 0
so, u = -7/5 or u=1
That means

x+5 = -7/5
x = -32/5

x+5 = 1
x = -4