f(x)=2-3x
f(x)=-2x+2
f(x)=x^3+1
f(x)=-x^2-2
f(x)=x^2+3x+4
f(x)=-x^3-2
f(x)=x^3+2x^2+6x+5
f(x)=-2x
f(x)=1/3 x+2
f(x)=x^2+3
