(1/3)x^3+x^2+C=(2/3)x^3+x^2+C x^2+2x=2x^2+2X x+2=2x+2 x=2x 1=2 there is the problem, first of all, the first line wil only work if C and X both equil 0 wich means that x=2x wont work because for that x must equil 1. Face it, you cant make 1=2 no matter what you try