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.  

Instead of finding all of the factors of -150, lets do this a bit more intelligently. Notice that 25 and 5 are both multiple of 5. This gives us the opportunity to substitute $t=5x$
$$25x^2+5xy-6y^2=(5x)^2+(5x)y-6y^2=t^2+ty-6y^2=\dots$$
After factoring, just substitute the $5x$ back in.
