若f[g(x)]=6x+3,且g(x)=2x+1,則f(x)=???答案是3X我想要解題過程擺脫各位啦

熱心網友

f[g(x)]=6x+3,且g(x)=2x+1,則f(x)=???解:f[g(x)]=3(2x+1)=3g(x),故f(x)=3x另解:設u=g(x)=2x+1,則x=(u-1)/2, f(u)=6*[(u-1)/2]+3=3u,即f(x)=3x