Consider the equations $\displaystyle 12x^2-4xy+11y^2=64$ and $\displaystyle 16^2x-9xy+11y^2=78$

By letting $\displaystyle y=mx$, show that $\displaystyle 7m^2+12m-4=0$ and thus solve the equation

okay, can you help me with this equation and also can someone tell me why it is neccesary to put in the form of y=mx?