How do I solve an equation with a variable in the numerator?

by AVReidy
Tags: equation, numerator, solve, variable
AVReidy is offline
Sep13-11, 02:29 PM
P: 49
1. The problem statement, all variables and given/known data

I just missed a 16-point question on a quiz because I didn't know how to separate the variable. It was an absolute value equation, but I just need to know how to deal with a variable in a fraction. Here's what it looked like:

2. Relevant equations

(5x+10)/2 = 20

3. The attempt at a solution
I tried multiplying everything by the denominator, but I'm not sure if or why that works. Any help would be greatly appreciated, thanks!
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Borek is offline
Sep13-11, 02:32 PM
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Multiplying by denominator should work. You can do anything that doesn't change the equality - that means adding, subtracting, multiplying or dividing both sides of the equation by the same thing.

Or you could write the fraction as [itex]\frac {5x}{2} + \frac {10}{2}[/itex].
AVReidy is offline
Sep13-11, 04:02 PM
P: 49

J2R is offline
Sep16-11, 01:33 AM
P: 2

How do I solve an equation with a variable in the numerator?

The easiest way is to multiply both sides of the equation by the denominator. The reason why this works is because it doesn't change the equality.

(5x+10)/2 = 20
5x+10 = 40
5x = 30
x = 6

Even if the variable was in the denominator, you can still solve for the variable using the same steps.

2/(5x+10) = 20
2 = 100x + 200
-198 = 100x
-198/100 = x
x = -99/50

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