Question

can anyone explain this to me?

28(x+5)-70(x+5)^2=[14(x+5)] [2-5(x+5)]

Answer 1

where do get the 2-5 from?

Answer 2

To make it a little more readable, let's do this:
y=x+5

So:

28(x+5)-70(x+5)^2 ; we start with the left side of the eqn.

=28y-70y^2 ; use y=x+5
=(28y-70y^2)
=14 * ( 2y - 5y^2 ) ; take 14 out of the parantheses
=14y * ( 2 - 5y ) ; take y out of the parantheses

=[14(x+5)] [2-5(x+5)] ; and we ended up with the right side of eqn.