Using grouping method, we have:

- Product of the outer 2 terms is: (4
*r*^{2})(−3*s*^{2}) = −12*r*^{2}*s*^{2} - Inner term: 11
*r**s*

So we are looking for 2 terms whose **product** is −12*r*^{2}*s*^{2}and whose **sum** is 11*r**s*.

Those 2 terms will be 12*rs* and *−rs.*

So we can factor our trinomial as follows:

4*r*^{2} + 11*rs ** *− 3*s*^{2}

= 4

r^{2}+ 12rs−rs− 3s^{2}= (4

r^{2}+ 12rs) − (rs+ 3s^{2})= 4

r(r+ 3s) −s(r+ 3s)= (4

r−s)(r+ 3s)