Find the LCD of the rational expressions.

Adding and Subtracting Rational Expressions? Algebra II? Help?

• 1. (7 / t) + (2 / t) 2. (11 / 5x) - (1 / 5x) 3. (5x+4 / 6x+5) + (x+1 / 6x+5) 4. (x^2 / x+5) - (25 / x+5) Find the least common denominator for each group of rational expressions. 5. (5 / 18x^2y^3) , (-3 / 24x^4y^5) 6. (9 / k+3) , (3 / k) 7. (17 / 3r-21) , (9 / r-7) 8. (x / x^2-81) , (3x / x^2+18x+81) Add or subtract as indicated. Write all answers in lowest terms. 9. (5 / x) + (9 / 4x) 10. (3 / x-3) - (1 / x) 11. (2 / 4-x) + (5 / x-4) 12. (5 / 12+4x) - (7 / 9+3x) 13. (5 / x^3-y^3) + (3 / x^2+xy+y^2) 14. (4a / a^2-ab-2b^2) - (6b / a^2+4ab+3b^2) Any help is greatly appreciated! Thanks :) - Kady.

• Answer:

  I'm sorry about the way the answer's coming, I don' know what happened to my computer... 1. (7 / t) + (2 / t) = 9/t 2. (11 / 5x) - (1 / 5x)=10/5x=2/x 3. (5x+4 / 6x+5) + (x+1 / 6x+5)=(5x+4-x-1)/(6x+5)= (4x+3)/(6x+5) 4. (x^2 / x+5) - (25 / x+5)=(x^2-25)/(x+5)= ((x+5)*(x-5))/(x+5)=x-5 5. (5 / 18x^2y^3) , (-3 / 24x^4y^5) 1/6x^2y^3 6. (9 / k+3) , (3 / k) 3 7. (17 / 3r-21) , (9 / r-7) 1/(r-7) 8. (x / x^2-81) , (3x / x^2+18x+81) (x/((x-9)*(x+9)),(3x/(x+9)^2) x/(x+9) 9. (5 / x) + (9 / 4x) =(20+9)/4x=29/4x 10. (3 / x-3) - (1 / x) = (3x-x+3)/(x*(x-3))= (2x+3)/(x^2-3x) 11. (2 / 4-x) + (5 / x-4) = (2x-8+20-5x)/((4-x)*(x-4)) 12. (5 / 12+4x) - (7 / 9+3x)= (45+15x-84+28x)/((12+4x)* (9+3x))= (43x-39)/(108+72x+12x^2) 13. (5 / x^3-y^3) + (3 / x^2+xy+y^2)= (5/((x-y)*(x^2+xy+y^2))) + (3 / x^2+xy+y^2) = (5+3x-3y)/(x^3-y^3)