To solve this problem, we need to identify an #a# and a #b# such that #ab=-28# and #a+b=-3#. Let's first list out the factors of 28 and see which ones add up to -3 (Ones that don't work = red; one that works = blue):

#color(red)(1 and 28)#

#color(red)(2 and 14)#

#color(blue)(4 and 7)#

We have found our pair! -4 and 7! So now, we need to write the original problem into a #(x+a)(x+b)# format. We have two ways of writing this:

Either #(x+4)(x-7)# or #(x-7)(x+4)# but they're both the same due to the Commutative Property of Multiplication.