Factor polynomial completely:
9y^2 - 25yz -6z2
Note that the coefficient of 9y^2 has factors of 3 or 9, while 3 is a factor of 6z^2. Since 3 is not a common factor of the expression, we conclude that 9 (in 9y^2) and 3 (in 6z^2) are in different factors.
Start with:
(9y 2z)(y 3z)
There has to be 1 negative sign out of the two factors (since the z^2 term is negative. That leaves us with one of two choices +/- or -/+.
Can you figure that out from here?