1
$\begingroup$

I am too rusty in algebra.
I have as input in a program numbers $a$ and $b$.
I am trying to find them using the below relation:

$a + b = X$ $ab=Y$

and $X$ and $Y$ are known numbers in my program.

I can't remember how to derive $a$ or $b$.

I get something like $a^{2}-aX+Y=0$ but cant't remember how to make it so that it is something like $a=....$ ; an $b=....$ ; in my program.

Any help please?

  • 1
    From there, you could use the quadratic equation.2012-04-23

1 Answers 1

2

$a = \dfrac{X +\sqrt{X^2 - 4Y}}{2}; b = \dfrac{X -\sqrt{X^2 - 4Y}}{2}$

  • 0
    This comes from the quadratic formula. You correctly recalled $a^2 - Xa + Y = 0$ and then I used the quadratic formula (and the fact that $a + b = X$)2012-04-23