for example, there is a function f(x)= x^{3}+ax^{2}+bx+c=0 with roots Q,W,E

then teachers told me that by substituting y=x^{2}, then we can find out f(y)=0 s.t. it has roots Q^{2},W^{2},E^{2 }but why such substition can help us to find out equations with root Q^{2},W^{2},E^{2}? What are the reasons behind?

Thanks for your kind helpings