What multiplies to 20 but adds to be -9?

Answer 1

Let the number be 'm' & 'n'

Hence

mn = 20

m + n = -5

m = -5 -n

Substitute

n(-5-n) = 20

-5n - n^2 = 20

n^2 + 5n + 20 = 0

It is now in quadratic form , so use quadratic eq'n

n = { - 5 +/- sqrt[(5_^2 - 4(1)(20)]} / 2(1)

n = { - 5 +/- sqrt[25 - 80]}/ 2

n = { - 5 +/'- sqrt[-80]} / 2

This is unreseolved because you cannot take the square root of a negative number.

5

Answer 2

11

Answer 3

-4*-5=20 -4+(-5)=-9