If f(x)=x2, for x≥0x, for x<0, then fof(x) is given by
x2 for x≥0,x for x<0
x4 for x≥0,x2 for x<0
x4 for x≥0,−x2 for x<0
x4 for x≥0,x for x<0
f(f(x))=(f(x))2, for f(x)≥0f(x), for f(x)<0
=x22,x2≥0,x≥0x2,x≥0,x<0x2,x2<0,x≥0x,x<0,x<0=x4,x≥0x,x<0