1. ## Solving a quadratic equation

$\displaystyle 30/x^2 = 1 - 7/x$

I know I need to multiply 30 by x and then 7 by x^2, but what do I need to do with the 1?

Thanks

2. Originally Posted by Local_lunatic
$\displaystyle 30/x^2 = 1 - 7/x$

I know I need to multiply 30 by x and then 7 by x^2, but what do I need to do with the 1?

Thanks
Mutiply everything by $\displaystyle x^2$ and see what you get.

3. Originally Posted by ThePerfectHacker
Mutiply everything by $\displaystyle x^2$ and see what you get.
$\displaystyle 30/x^2 = 1- 7/x$
$\displaystyle 30 = x^2 - 7x$
$\displaystyle x^2 - 7x - 30 =0$
$\displaystyle (x+3) (x-10) =0$
$\displaystyle x=-3$ or $\displaystyle x=10$

How do you know to multiply it by x^2? Is there a rule or something to follow?

Thanks

4. Originally Posted by Local_lunatic
$\displaystyle 30/x^2 = 1- 7/x$
$\displaystyle 30 = x^2 - 7x$
$\displaystyle x^2 - 7x - 30 =0$
$\displaystyle (x+3) (x-10) =0$
$\displaystyle x=-3$ or $\displaystyle x=10$

How do you know to multiply it by x^2? Is there a rule or something to follow?

Thanks
Since there is an $\displaystyle x^2$ on the bottom of the fraction, to get it to disappear and have a simpler equation to work with, you multiply every term by it.

5. Originally Posted by Adrienne
Since there is an $\displaystyle x^2$ on the bottom of the fraction, to get it to disappear and have a simpler equation to work with, you multiply every term by it.
Of course it is, I was thinking that it was x not x^2.. Sometimes I swear my brain isn't switched on!

Thanks both of you for your help