4)(x+2)^2/2 - (x^2-4)/4 - (x-2)^2/8 = x^2/8
(4(x+2)^2 - 2(x^2-4) - (x-2)^2- x^2)/8=0
4(x+2)^2 - 2(x^2-4) - (x-2)^2- x^2)=0
4(x^2+2x+4) - 2x^2+8 - (x^2-2x+4) - x^2 = 0
4x^2+8x+16 - 2x^2+8 - x^2+2x - 4 - x^2 = 0
10x +20 = 0
10(x + 10) = 0
x + 10 = 0
x = -10.
ОТВЕТ: -10.