Question

One number is 9 more than another number. If the product of the two numbers is -20, how do you find both numbers?

Answer 1

One number be `-5` and another number be `4`
[or]
One number be `-4` and another number be `5`

Explanation:

Let the given number be `a`
Then the next number be `b`

`b = a+9`

Form the equation -

`a xx (a+9)=-20`

Solve it for `a`

`a^2+9a=-20`
`a^2+9a+20=0`
`a^2+5a+4a+20=0`
`a(a+5)+4(a+5)=0`
`(a+5)(a+4)=0`

`a+5=0`
`a=-5`
`a+4=0`
`a=-4`

If `a=-5`

`b=a+9`
`b=-5+9=4`

If `a=-4`

`b=a+9`
`b=-4+9=5`

One number be `-5` and another number be `4`
[or]
One number be `-4` and another number be `5`