Question 1210241
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what two numbers multiply to -16 and add to 15
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<U>Answer</U>.  The numbers are 16 and -1.


Here are two ways to solve it.


<pre>
First way is to guess it mentally. Usually, it requires several seconds and does not require writing.


Another way is to introduce x for one number, 15-x for another number,
and then to write and to solve this equation for the product 

    x*(15-x) = -16,

    15x - x^2 = - 16,

    x^2 - 15x - 16 = 0,

    (x-16)*(x+1) = 0.      <<<---===  factoring


It gives the answer algebraically:  the numbers are 16 and -1.
</pre>

Solved.