Answer:
(y-7x)(y+8x)
The attachment is checking the work
Answer: I got (y-8x)(y-7x) by factoring out the factors of 56, that have a sum of -1.
8 and 7 are factors of 56 when you multiply them and to get a sum of -1, 8 should change to negative. 7 + -8 = -1
