There are no zeroes for an expression, only for equations.
Assuming equation to be
<span>−7x^2 − 91x − 280=0
-7(x^2+13x+40)=0
-7(x+8)(x+5)=0
by the zero product properties,
x+8=0 => x=-8
or
x+5=0 => x=-5</span>
Answer:

Step-by-step explanation:
Let the
be the first number,
be the second number and
be the product of the first and second number.
i.e




Now,

Hence, 
8k-4k+4+7-k =
8k-4k-k+4+7 =
3k+11
The sum of 2 opposites =0
X+6 would now equal 0
So your answer is 0