find two integers with a product of 16(-5)=-80 (,) and a sum of -16
let the two numbers be a and b.
Product: a * b = -80
Sum: a + b = -16
From the sum, a = -16 - b
Substituting for a = -16 - b into the product,
(-16 - b) * b = -80 multiply out the bracket
-16b - b^2 = -80 rearrange and simplify
b^2 + 16b - 80 = 0 factorise the quadratic
(b - 4)(b + 20) = 0
Hence b = 4, or b = -20
Using a = -16 - b,
Then a = -20, or a = 4
Thus the two numbers are : 4 and -20