2x^2+2x-40=0
2x^2+10x-8x-40=0
2x(x+5)-8(x+5)=0
(2x-8)(x+5)=0
2(x-4)(x+5)=0
x=-5 and 4
If you graph it, the zeros are just the values of x when the curve meets the x axis...
2x (Multiplied by) 6
You cannot combine 2x and 6 because x is an unknown variable that is attached to a coefficient. Hope this helps!
ANSWER
We need to add half the coefficient of
all square.

EXPLANATION
Given the equation,
.
We compare to the general equation,

This means that;

To complete the square we add, 
That is
.
Hence the number to be added to both sides is
.
Note that before we complete the square, the coefficient of the term in
must always be 1.
Answer:
Its either A or B I believe it's A srry if im wrong.