factor the following expression $25x^2 +5xy -6y^2$ How to factor
$$25x^2 +5xy -6y^2$$
I tried with $5x(5x+y)-6y^2$. I'm stuck here. 
I can't continue.  

The trick here is to manipulate the expression $25x^2+5xy-6y^2$. Try the following:
\begin{align}
25x^2+5xy-6y^2 &= 25x^2+15xy-10xy-6y^2\tag{manipulate}\\[0.5em]
               &= 5x(5x+3y)-2y(5x+3y)\tag{factoring}\\[0.5em]
               &= (5x-2y)(5x+3y)\tag{group}
\end{align}
Is this clear now?
