Quadratics with fractions

spear33

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Jan 30, 2006
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For this problem I'm allowed to solve by factoring, complete the square or use the quadratic equation.

2 - 5/k + 2/k^2=0

The main problem is I'm not sure what to do with the fractions. Any help would be much appreciated.
 
You've followed the tutor's instructions (to multiply through by k<sup>2</sup> to clear out the denominators); now rearrange the quadratic in the usual form, and apply the usual methods for solving. The Quadratic Formula, for instance, will work, as will factoring.

Eliz.
 
If you multiply both sides by k^2 is it supposed to look like this...

2 - 5/k + 2 = 0 * k^2

I think I'm just making this more complicated than it actually is.
 
spear33 said:
If you multiply both sides by k^2 is it supposed to look like this: 2 - 5/k + 2 = 0 * k^2
How are you getting that (2)(k<sup>2</sup>) equals 2, or that (-5/k)(k<sup>2</sup> is still -5/k...? Did you forget that "multiplying through on both sides" means "multiplying through onto every term on each side"?

Note: (0)(k<sup>2</sup>) = 0.

Eliz.

Edit: Correcting formatting.
 
To do it literally, multiplying both sides by \(\displaystyle \mbox{k^2}\) is to go:

\(\displaystyle \mbox{ k^2\left(2 - \frac{5}{k} + \frac{2}{k^2}\right) = k^2(0) }\)

where \(\displaystyle \mbox{k^2(0) = 0}\) and \(\displaystyle \mbox{ k^2\left(2 - \frac{5}{k} + \frac{2}{k^2}\right)}\) expands to?
 
Brilliant. Now can you solve for k?

(You've always got the quadratic formula to fall back on.)
 
k= -5 plus or minus the square root of 41 divided by 4

Sorry I dont know how to make it into an image file or anything like that.

[Edit] Just caught my mistake its 9 not 41
 
Yeah, actually -5 was written as a positive 5 on my paper, but in my rush to post it I thought I accidently forgot to put the - in front on my paper. Anyways thanks for all the help and I'm sure I'll be back here sometime this semester (probably tonight).
 
spear33 said:
k= -5 plus or minus the square root of 41 divided by 4
Sorry I dont know how to make it into an image file or anything like that.
[Edit] Just caught my mistake its 9 not 41
That should be +5 : -(-5) = 5; so:
k = [5 +- sqrt(9)] / 4 : capish?
 
spear33 said:
I dont know how to make it into an image file or anything like that.
No prob; no worries. But if you would like to learn how to format with LaTeX (and if I can do it, it can't be that hard!), then follow the lower links in the "Forum Help" pull-down menu at the very top of the page.

Eliz.
 
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