What two numbers add to - 7 and multiply to 12?

A+b=-7 and ab=12

from the first we can say a=-b-7 and using this value for a in the second we get:

(-b-7) b=12

-b^2-7b=12

b^2+7b+12=0

b^2+3b+4b+12=0

b (b+3) + 4 (b+3) = 0

(b+4) (b+3) = 0

So the numbers are - 3 and - 4