Question

Y * x = 20

y + x = 9

what numbers are y and x equal to?

Answer 1

`y = 9 - x`
Substitute into

`y * x = 20 \\ (9 - x) * x = 20 \\ { - x}^(2) + 9x = 20 \\ {x}^(2) - 9x + 20 = 0 \\ (x - 5)(x -4) = 0 \\ x = 5 \: or \: x = 4`
When x = 5,

`y = 9 - 5 \\ y = 4`
When x = 4,

`y = 9 - 4 \\ y = 5`

x = 5, y = 4
x = 4, y = 5

Hope this helps. - M