∣x-x2-2∣>x2-3x-4
x-x2-2>x2-3x-4 x-x2-2x2+x2+2-4 x-3x2x2-2 -2x(x2-1)/2 x>3
当(x2-1)/2 >=3时 则x>3
当(x2-1)/2 (x2-1)/2