Subtracting Rational Expressions

This Movie (Quicktime)
will show you how to subtract rational expressions with unlike denominators.

The following is the movie transcript.

Hi, my name is Therese and this podcast presentation is about Subtracting Rational Expression with unlike Denominators.

To subtraction a rational expression with unlike denominators you must follow these four steps.
• Find a common denominator
• Change each fraction to an equivalent fraction
• Subtract the numerators while keeping the same denominator
• Reduce if possible

The problem we are going to subtract is five over x minus three over four x. To subtract this rational expression with unlike denominators, you must first establish the common denominator, which in this case is four x. After identifying the common denominator you should change each fraction to an equivalent fraction with the common denominator of four x.
To change the first fraction to the common denominator we will multiply the numerator by four and the denominator by four. Since the second fraction already has the common denominator of four x we don’t need to change it.
Now we will multiply the fraction: four times five gives us twenty and four x gives us four x, subtracting three over four x. Next we will subtract the numerator while keeping the same denominator twenty minus three gives us seventeen over four x. And since we can not reduce the final answer is seventeen over four x.
This concludes the presentation on how to subtract rational expressions with unlike denominator.

End Movie Transcript

Posted at 11:26AM Dec 05, 2006 by llinebarger in Intermediate Algebra  |