f（x）=x²-1,g（x）=x-1＞0,x＞0 2-x＜0,x＜0,求f[g(2)] g[f(2)],f[g(x)],g[f(x)]

f（x）=x²-1,g（x）=x-1＞0,x＞0 2-x＜0,x＜0,求f[g(2)] g[f(2)],f[g(x)],g[f(x)]
f（x）=x²-1,g（x）=x-1＞0,x＞0 2-x＜0,x＜0,求f[g(2)] g[f(2)],f[g(x)],g[f(x)]

f（x）=x²-1,g（x）=x-1＞0,x＞0 2-x＜0,x＜0,求f[g(2)] g[f(2)],f[g(x)],g[f(x)]
g(2)=2-1=1
f(g(2))=f(1)=0

f(2)=2²-1=3
∴g(f(2))=g(3)=3-1=2

当x>0时 f(g(x))=(x-1)²-1=x²-2x
当x0
∴x>1或x