已知f(x)=x^2-1,g(x)=x-1(x小于0)或2-x(x大于0),求f[g(x)]与[f(x)]

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已知f(x)=x^2-1,g(x)=x-1(x小于0)或2-x(x大于0),求f[g(x)]与[f(x)]

f[g(x)]=(x-1)^2-1=x^2-2x x0
g[f(x)]=x^2-1-1=x^2-2 (x^2-10)

f[g(x)]=(x-1)^2-1=x^2-2x (x小于0)
f[g(x)]=(2-x)^2 -1= x^2-4x+3 (x大于0),
[f(x)]=x^2-1 (x>1或x<-1)
[f(x)]=-x^2+1 (-1

f[g(x)]=(x-1)^2-1 (x小于0)或
f[g(x)]=(2-x)^2-1 (x大于0);
当f(x)=x^2-1小于0,即x小于1或大于-1时,g[f(x)]=(x^2-1)-1=x^2-2
当f(x)=x^2-1大于0,即x大于1或小于-1时,g[f(x)]=2-(x^2-1)=3-x^2