Question

Write the expression 5x(x + 9) − 7(x + 9) in complete factored form

Answer 1

So the problem ask to complete the factored form in the equation but first of the you must keep in mind that the common of the two is (x+9), so it means that you can rewrite the equation in to a simplest form and that would be (x+9)(5x-7). I hope you are satisfied with my answer and feel free to ask for more 

Answer 2

remember the distributive property

a(b+c)=ab+ac

reverse it
ab+ac=a(b+c)
5x(x+9)-7(x+9)
notice that (x+9) is common to both, just like a

(5x-7)(x+9)