Posted by **jazmin** on Friday, October 8, 2010 at 8:06am.

can you answer this please about sums and differences of a rational algebraic expression this is the problem 5/x-7 - x-1/x-7 - 2+x/x-7 another is x+1/2 - x-2/3 + 2x-1/9 another is 2x+3/3 - 3x-1/2 + x-4/12

- math -
**Reiny**, Friday, October 8, 2010 at 8:17am
did you mean

5/(x-7) - (x-1)/(x-7) - (2+x)/(x-7)

since you already have a common denominator, just add/subtract the numerators

= (5 - x + 1 - 2 - x)/(x-7)

= (4-2x)/(x-7)

for the second, your common denominator would be the LCM of 2,3, and 9 which would be 18

(x+1)/2 - (x-2)/3 + (2x-1)/9

= [9(x+1) - 6(x-2) + 2x-1 ] /9

= .....

third one is just as easy, the LCD is 12

- correction - math -
**Reiny**, Friday, October 8, 2010 at 10:14am
obviously I have a typo in the second question, should say ...

(x+1)/2 - (x-2)/3 + (2x-1)/18

= [9(x+1) - 6(x-2) + 2x-1 ] /18

= .....

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