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

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Answer 1 · 2017-01-10T05:37:11

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

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 $5$