Question 1025135
Polynomial equations, which have two answers. 
Equations in this form are likely (especially on a test) created by (x+a)(x+b)=0.
Either x+a=0 or x+b=0 

Given the simplicity of this problem what are the factors of 28 that have a difference of 3
28, 1 nope. 14, 2 nope, 7, 4 yes! 
We know that one must be negative and one positive. Since the second term in the original question si positive, the answers are a and b are 7 and -4.

Going back to find x, we have x+7=0 and x-4=0. Solving for x we get -7 and 4. 

Testing them in the original equation proves they are correct.