Решение:
$$(-x-8)(x-8)+x(x+16)$$$$x = -\frac{7}{8} = -0.875$$$$(-(-0.875)-8)((-0.875)-8) + (-0.875)((-0.875)+16) = $$$$(0.875-8)(-0.875-8) + (-0.875)(15.125) = $$$$(-7.125)(-8.875) + (-13.234375) = 63.234375 - 13.234375 = 50$$
Ответ: 50