Question

What two number multiply to -21 and add to 20

Answer 1

21 * (-1) = -21
21 + (-1) = 20

Answer 2

Answer:

-1 and 21

Step-by-step explanation:

Let the numbers be x and y.

x + y = 20

xy = -21

Solve the first equation for x and substitute in the second equation.

x = 20 - y

(20 - y)y = -21

20y - y^2 = -21

y^2 - 20y - 21 = 0

(y - 21)(y + 1) = 0

y - 21 = 0 or y + 1 = 0

y = 21 or y = -1

For y = 21:

x = 20 - y

x = 20 - 21

x = -1

For y = -1:

x = 20 - y

x = 20 - (-1)

x = 21

Solutions: (-1, 21) and (21, -1)

Answer: the numbers are -1 and 21