First Hello and welcome to the forum. You have been posting alot of questions. I would recommend you learn LaTex. See here http://www.mathhelpforum.com/math-help/f47/

Note you can also click on the math symbols to see the code that generated them.

Now onto your question.

Note that you have the system of equations.

and

This implies that

Now using this we get

Can you finish from here?