f(x)=4x+3,g(x)=x2,求f[f(1)],f[f(x)],f[g(2)],g[f(x)]
问题描述：
f(x)=4x+3,g(x)=x2,求f[f(1)],f[f(x)],f[g(2)],g[f(x)]
答
1、f(1)=4*1+3=7
所以f[f(1)]=f(7)=4*7+3=31
2、f[f(x)]
=f(4x+3)
=4*(4x+3)+3
=16x+15
3、g（2）=2^2=4
f[g(2)]=f(4)=4*4+3=19
4、g[f(x)]
=g(4x+3)
=(4x+3)^2
=16x^2+24x+9