Question

Factor by grouping
4c^2+9c-28
There is not a common denominator
so I think this should look like
(2c+3-4)^2 But the answer is wrong. Any takers

Answer 1

Factor by trinomial method. So multiple 4 and -28 together to get -112. Factors of -112 that add up to 9 are 16 and -7. So split the middle term with those numbers, so it's: 4c^2+16c-7c-28, then factor by grouping.

So 4c(c+4)-7(c+4), so it factors into (4c-7)(c+4)

Answer 2

get all the factors of 4(-28). and see which ones combine to get +9. Like spaceknight did :)