Question

若f(x+1)=x2+2x则f(x)=

拜托各位帮帮忙了,请把解题过程也给写出来,先在这里谢谢啦!

Answer 1

解：设x+1=t，则x=t-1，可得：
f(t)=(t-1)²+2(t-1)
=t²-2t+1+2t-2
=t²-1
因此，f(x)=x²-1。

Answer 2

f(x+1)=x2+2x
解：令t=x+1
那么x=t-1
f(x+1)=f(t)=x^2+2x=(t-1)^2+2(t-1)=t^2-1
即 f(t)=t^2-1

所以 f(x)=x^2-1

Answer 3

设x+1=t,则x=t-1
f(x)=(t-1)^2+2(t-1)
=t^2-2t+1+2t-2
t^2-1

Answer 4

fx+f=4x
fx =4x-f