What multiplies to get -1 and adds up to get -8?

Answer 1

-9

Answer 2

Let the number be 'm' & 'n'

Hence as multiples

mn = -1

m + n = -8

Let m = -8 -n

Substitute

n(-8 -n) = -1

-8n - n^2 = -1

n^2 + 8n - 1 = 0 4

This will not factor so apply the Quadratic Equation.

n = {-8 +/- sqrt{8^2 - 4(1)(-1)]} / 2(1)

n = {-8 +/- sqrt[64 + 4]} / 2

n = {-8 +/-sqrt[68]}/2

n = { - 8+/- 8.2462...} / 2

n = -4 +/- 4.1231....

n = - 8.1231.... & 0.1231. are the two numbers.