Question 973666: what multipies to get -12 but adds to get -21?
Answer by KMST(5328)   (Show Source):
You can put this solution on YOUR website! No pair of rational number factors will do that.
The answer would be the solutions to the quadratic equation  ,
which are given by  .
That is approximately 0.55667219 and -21.55667219.
Not all quadratic equations can be solved by factoring.
(It only works if the solutions are rational numbers, and it is easiest when they are integers).
However, there are two ways that work well to solve any quadratic equation.
You can solve any quadratic equation of the form  by using the quadratic formula:
 .
For ,  , so
 .
Also, you can solve any quadratic equation by completing the square",
without having to remember the quadratic formula.
(In some cases, it is easier than using the quadratic formula,
but this is not one of those cases).
In this case, you would do it like this:
 --->  --->  <---> .
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