设f(x)=kx+b
3f(x+1)-2f(x-1)=3*(k*(x+1)+b)-2*(k*(x-1)+b)
=3kx+3k+3b-2kx+2k-2b
=kx+5k-b
=2x+17
所以k=2
5k-b=17
k=2 b=-7
f(x)=2x-7