已知一次函數(shù)f(x)滿足f[f(x)]=4x+3,求f(x).
f(x)=2x+3或f(x)=-2x-3詳解:設(shè)f(x)=ax+b,則f[f(x)]=a(ax+b)+b=a^2*x+ab+b依題意a^2=4, ab+b=3解得(1)a=2,b=1或(2)a=-2,b=-3
