证明:若f(x)=ax+b 则f(x1+x2/2)=f(x1)+f(x2)/2

问题描述:

证明:若f(x)=ax+b 则f(x1+x2/2)=f(x1)+f(x2)/2

用带入法

f(x)=ax+b
f((x1+x2)/2)
=a((x1+x2)/2)+b
=ax1/2+ax2/2+b
[f(x1)+f(x2)]/2
=[ax1+b+ax2+b]/2
=ax1/2+ax2/2+b
所以
f(x1+x2/2)=[f(x1)+f(x2)]/2