Question

Find two integers whose sum is -13 and product is 40

Answer 1

-8 and -5

-8 x -5 = 40
-8 + (-5) = -13

Answer 2

Let us say, the numbers are "a" and "b"
their sum is -13
a + b = -13 

their product is 40
a * b = 40 $\bf \begin{cases} a+b=-13\\ a\cdot b=40\implies b=\frac{40}{a}\\ then\\ ------------\\ a+\boxed{b}=-13\implies a+\boxed{\frac{40}{a}}=-13 \end{cases}$

solve for "a",
what is "b"? well, b = 40/a :)