f(x)=(x²-2)☒(x-x²)
(x²-2)-(x-x²)≤1
2x²-x-3≤0
(2x-3)(x+1)≤0
-1≤x≤3/2
∴f(x)=(x²-2) -1≤x≤3/2
f(x)=(x-x²) x<-1∪x>3/2
