6x-(2x-5)=2(2x+4) = 6x - 2x + 5 = 4x + 8 = 6x - 2x - 4x = -5 + 8 = x=3
Ответ:
x*x+x=90
90-x=x*x
x+x=-1
x*x=-90
x=9 x=-10