f(x+2)=xˆ2+1,则f(x)=( ) (A)xˆ2+3 (B)xˆ2-1 (C)xˆ2-4x+5 (D)x

问题描述:

f(x+2)=xˆ2+1,则f(x)=( ) (A)xˆ2+3 (B)xˆ2-1 (C)xˆ2-4x+5 (D)x

令a=x+2
x=a-2
f(a)=(a-2)^2+1=a^2-4a+5
f(x)=x^2-4x+5
选C