subtracting rational expressions: 2x+3/x-1 - x-1/x+1, ....
- Thread starter chasann29
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Re: subtracting rational expressions
1) Fix your notation. The second one is okay, but that first one is no good. Put the parentheses where they belong.
2) You cannot find how to begin because you already know how to begin. Part of the point of teaching mathematics in a specific sequence is so that you will have the tools you need when the time comes. This is one of those times. You have added fractions many times before this day. Simply do it again. Common denominator? This should ring a bell?
Just Numbers
1/3 + 1/4 = ??
Common denominator of 12
4/12 + 3/12 = 7/12
Symbols that may or may not mean something
1/dog + 1/cat = ??
Common denominator of dog*cat
cat/(dog*cat) + dog/(dog*cat) = (cat + dog)/(dog*cat)
Now your problem #1
(2x+3)/(x-1) - (x-1)/(x+1) -- Note added parentheses and corrected spacing to add clarity to the problem statement.
Common denominator (x-1)(x+1)
[(2x+3)*(x+1)]/[(x-1)*(x+1)] - [(x-1)*(x-1)]/[(x+1)*(x-1)] = {[(2x+3)*(x+1)] - [(x-1)*(x-1)]}/[(x+1)*(x-1)] =
Oh, you do the rest...
1) Fix your notation. The second one is okay, but that first one is no good. Put the parentheses where they belong.
2) You cannot find how to begin because you already know how to begin. Part of the point of teaching mathematics in a specific sequence is so that you will have the tools you need when the time comes. This is one of those times. You have added fractions many times before this day. Simply do it again. Common denominator? This should ring a bell?
Just Numbers
1/3 + 1/4 = ??
Common denominator of 12
4/12 + 3/12 = 7/12
Symbols that may or may not mean something
1/dog + 1/cat = ??
Common denominator of dog*cat
cat/(dog*cat) + dog/(dog*cat) = (cat + dog)/(dog*cat)
Now your problem #1
(2x+3)/(x-1) - (x-1)/(x+1) -- Note added parentheses and corrected spacing to add clarity to the problem statement.
Common denominator (x-1)(x+1)
[(2x+3)*(x+1)]/[(x-1)*(x+1)] - [(x-1)*(x-1)]/[(x+1)*(x-1)] = {[(2x+3)*(x+1)] - [(x-1)*(x-1)]}/[(x+1)*(x-1)] =
Oh, you do the rest...
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I'm sorry to hear that the text is confusing and that your instructor hasn't covered this. :shock:chasann29 said:
Assuming you're "okay" with numerical fractions (with their common denominators, etc) and with simplifying and multiplying rational expressions, try some online lessons to fill in what your instructor didn't explain:
. . . . .Google results for "subtracting rational expressions"
Have fun!
Eliz.