I will show you a trick that solves all this kind of problems.
15X^{2 }+ 11X  56
A quadratic like this can only be factorable, if There exist 2 rational numbers whose Sum is 11, and
their product is  15 * 56
So we rite 15 * 56 as product of its factor
15 * 56 = 3 * 5 * 7 * 8 = 15 * 56 = 35 * 24 =
Now we see that the difference of 35 and 24 is 11
15 X^{2 }+ 35X  24X 56 ( break up 11X into 35X 24X)
5X( 3X +7 )  8 ( 3X + 7) , Now 2 terms have common factor of (3X +7 )
( 3X + 7 ) ( 5X  8 ) This is the final answer.
Oct 9

Parviz F.
Comments