factorization

28x²+24xy-27y²

I am looking for 2 numbers that add to 24 and multiply to  -28*27

a+b=24   and ab=-28*27

solving this simultaneously I get a and b are  -18 and 42

$$\\28x^2-18xy+42xy-27y^2\\ =2x(14x-9y)+3y(14x-9y)\\ =(2x+3y)(14x-9y)$$

B  

$$\\28x^2+24xy-27y^2-6x-9y\\ =(2x+3y)(14x-9y)-3(2x+3y)\\ =(2x+3y)(14x-9y-3)$$