Answer :
There are no zeroes for an expression, only for equations.
Assuming equation to be
−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
Assuming equation to be
−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