f(x)=kx+b
所以2f(2)-3f(1)
=2(2k+b)-3(k+b)
=k-b=5 (1)
2f(0)-f(-1)
=2b-(-k+b)
=k+b=1 (2)
联立,解得k=3,b=-2
f(x)=3x-2