已知函数f(x)=3x^2+1,g(x)=2x-1.求f[g(x)]和g[f(x)]
问题描述:
已知函数f(x)=3x^2+1,g(x)=2x-1.求f[g(x)]和g[f(x)]
答
f[g(x)]=f(2x-1)=3(2x-1)^2+1=3(4x^2-4x+1)+1=12x^2-12x+4
g[f(x)]=g(3x^2+1)=2(3x^2+1)-1=6x^2+1