Practice Makes Perfect
Add and Subtract Rational Expressions with a Common Denominator
In the following exercises, add.
1. \(\dfrac{2}{15}+\dfrac{7}{15}\)
- Answer
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\(\dfrac{3}{5}\)
2. \(\dfrac{7}{24}+\dfrac{11}{24}\)
3. \(\dfrac{3c}{4c−5}+\dfrac{5}{4c−5}\)
- Answer
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\(\dfrac{3c+5}{4c−5}\)
4. \(\dfrac{7m}{2m+n}+\dfrac{4}{2m+n}\)
5. \(\dfrac{2r^2}{2r−1}+\dfrac{15r−8}{2r−1}\)
- Answer
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\(r+8\)
6. \(\dfrac{3s^2}{3s−2}+\dfrac{13s−10}{3s−2}\)
7. \(\dfrac{2w^2}{w^2−16}+\dfrac{8w}{w^2−16}\)
- Answer
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\(\dfrac{2w}{w−4}\)
8. \(\dfrac{7x^2}{x^2−9}+\dfrac{21x}{x^2−9}\)
In the following exercises, subtract.
9. \(\dfrac{9a^2}{3a−7}−\dfrac{49}{3a−7}\)
- Answer
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\(3a+7\)
10. \(\dfrac{25b^2}{5b−6}−\dfrac{36}{5b−6}\)
11. \(\dfrac{3m^2}{6m−30}−\dfrac{21m−30}{6m−30}\)
- Answer
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\(\dfrac{m−2}{2}\)
12. \(\dfrac{2n^2}{4n−32}−\dfrac{18n−16}{4n−32}\)
13. \(\dfrac{6p^2+3p+4}{p^2+4p−5}−\dfrac{5p^2+p+7}{p^2+4p−5}\)
- Answer
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\(\dfrac{p+3}{p+5}\)
14. \(\dfrac{5q^2+3q−9}{q^2+6q+8}−\dfrac{4q^2+9q+7}{q^2+6q+8}\)
15. \(\dfrac{5r^2+7r−33}{r^2−49}−\dfrac{4r^2+5r+30}{r^2−49}\)
- Answer
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\(\dfrac{r+9}{r+7}\)
16. \(\dfrac{7t^2−t−4}{t^2−25}−\dfrac{6t^2+12t−44}{t^2−25}\)
Add and Subtract Rational Expressions whose Denominators are Opposites
In the following exercises, add or subtract.
17. \(\dfrac{10v}{2v−1}+\dfrac{2v+4}{1−2v}\)
- Answer
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\(4\)
18. \(\dfrac{20w}{5w−2}+\dfrac{5w+6}{2−5w}\)
19. \(\dfrac{10x^2+16x−7}{8x−3}+\dfrac{2x^2+3x−1}{3−8x}\)
- Answer
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\(x+2\)
20. \(\dfrac{6y^2+2y−11}{3y−7}+\dfrac{3y^2−3y+17}{7−3y}\)
21. \(\dfrac{z^2+6z}{z^2−25}−\dfrac{3z+20}{25−z^2}\)
- Answer
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\(\dfrac{z+4}{z−5}\)
22. \(\dfrac{a^2+3a}{a^2−9}−\dfrac{3a−27}{9−a^2}\)
23. \(\dfrac{2b^2+30b−13}{b^2−49}−\dfrac{2b^2−5b−8}{49−b^2}\)
- Answer
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\(\dfrac{4b−3}{b−7}\)
24. \(\dfrac{c^2+5c−10}{c^2−16}−\dfrac{c^2−8c−10}{16−c^2}\)
Find the Least Common Denominator of Rational Expressions
In the following exercises, a. find the LCD for the given rational expressions b. rewrite them as equivalent rational expressions with the lowest common denominator.
25. \(\dfrac{5}{x^2−2x−8},\dfrac{2x}{x^2−x−12}\)
- Answer
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a. \((x+2)(x−4)(x+3)\)
b. \(\dfrac{5x+15}{(x+2)(x−4)(x+3)}\),
\(\dfrac{2x^2+4x}{(x+2)(x−4)(x+3)}\)
26. \(\dfrac{8}{y^2+12y+35},\dfrac{3y}{y^2+y−42}\)
27. \(\dfrac{9}{z^2+2z−8},\dfrac{4z}{z^2−4}\)
- Answer
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a. \((z−2)(z+4)(z−4)\)
b. \(\dfrac{9z−36}{(z−2)(z+4)(z−4)}\),
\(\dfrac{4z^2−8z}{(z−2)(z+4)(z−4)}\)
28. \(\dfrac{6}{a^2+14a+45},\dfrac{5a}{a^2−81}\)
29. \(\dfrac{4}{b^2+6b+9},\dfrac{2b}{b^2−2b−15}\)
- Answer
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a. \((b+3)(b+3)(b−5)\)
b. \(\dfrac{4b−20}{(b+3)(b+3)(b−5)}\),
\(\dfrac{2b^2+6b}{(b+3)(b+3)(b−5)}\)
30. \(\dfrac{5}{c^2−4c+4},\dfrac{3c}{c^2−7c+10}\)
31. \(\dfrac{2}{3d^2+14d−5},\dfrac{5d}{3d^2−19d+6}\)
- Answer
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a. \((d+5)(3d−1)(d−6)\)
b. \(\dfrac{2d−12}{(d+5)(3d−1)(d−6)}\),
\(\dfrac{5d^2+25d}{(d+5)(3d−1)(d−6)}\)
32. \(\dfrac{3}{5m^2−3m−2},\dfrac{6m}{5m^2+17m+6}\)
Add and Subtract Rational Expressions with Unlike Denominators
In the following exercises, perform the indicated operations.
33. \(\dfrac{7}{10x^2y}+\dfrac{4}{15xy^2}\)
- Answer
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\(\dfrac{21y+8x}{30x^2y^2}\)
34. \(\dfrac{1}{12a^3b^2}+\dfrac{5}{9a^2b^3}\)
35. \(\dfrac{3}{r+4}+\dfrac{2}{r−5}\)
- Answer
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\(\dfrac{5r−7}{(r+4)(r−5)}\)
36. \(\dfrac{4}{s−7}+\dfrac{5}{s+3}\)
37. \(\dfrac{5}{3w−2}+\dfrac{2}{w+1}\)
- Answer
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\(\dfrac{11w+1}{(3w−2)(w+1)}\)
38. \(\dfrac{4}{2x+5}+\dfrac{2}{x−1}\)
39. \(\dfrac{2y}{y+3}+\dfrac{3}{y−1}\)
- Answer
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\(\dfrac{2y^2+y+9}{(y+3)(y−1)}\)
40. \(\dfrac{3z}{z−2}+\dfrac{1}{z+5}\)
41. \(\dfrac{5b}{a^2b−2a^2}+\dfrac{2b}{b^2−4}\)
- Answer
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\(\dfrac{b(5b+10+2a^2)}{a^2(b−2)(b+2)}\)
42. \(\dfrac{4}{cd+3c}+\dfrac{1}{d^2−9}\)
43. \(\dfrac{−3m}{3m−3}+\dfrac{5m}{m^2+3m−4}\)
- Answer
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\(-\dfrac{m}{m+4}\)
44. \(\dfrac{8}{4n+4}+\dfrac{6}{n^2−n−2}\)
45. \(\dfrac{3r}{r^2+7r+6}+\dfrac{9}{r^2+4r+3}\)
- Answer
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\(\dfrac{3(r^2+6r+18)}{(r+1)(r+6)(r+3)}\)
46. \(\dfrac{2s}{s^2+2s−8}+\dfrac{4}{s^2+3s−10}\)
47. \(\dfrac{t}{t−6}−\dfrac{t−2}{t+6}\)
- Answer
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\(\dfrac{2(7t−6)}{(t−6)(t+6)}\)
48. \(\dfrac{x−3}{x+6}−\dfrac{x}{x+3}\)
49. \(\dfrac{5a}{a+3}−\dfrac{a+2}{a+6}\)
- Answer
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\(\dfrac{4a^2+25a−6}{(a+3)(a+6)}\)
50. \(\dfrac{3b}{b−2}−\dfrac{b−6}{b−8}\)
51. \(\dfrac{6}{m+6}−\dfrac{12m}{m^2−36}\)
- Answer
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\(\dfrac{−6}{m−6}\)
52. \(\dfrac{4}{n+4}−\dfrac{8n}{n^2−16}\)
53. \(\dfrac{−9p−17}{p^2−4p−21}−\dfrac{p+1}{7−p}\)
- Answer
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\(\dfrac{p+2}{p+3}\)
54. \(\dfrac{−13q−8}{q^2+2q−24}−\dfrac{q+2}{4−q}\)
55. \(\dfrac{−2r−16}{r^2+6r−16}−\dfrac{5}{2−r}\)
- Answer
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\(\dfrac{3}{r−2}\)
56. \(\dfrac{2t−30}{t^2+6t−27}−\dfrac{2}{3−t}\)
57. \(\dfrac{2x+7}{10x−1}+3\)
- Answer
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\(\dfrac{4(8x+1)}{10x−1}\)
58. \(\dfrac{8y−4}{5y+2}−6\)
59. \(\dfrac{3}{x^2−3x−4}−\dfrac{2}{x^2−5x+4}\)
- Answer
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\(\dfrac{x−5}{(x−4)(x+1)(x−1)}\)
60. \(\dfrac{4}{x^2−6x+5}−\dfrac{3}{x^2−7x+10}\)
61. \(\dfrac{5}{x^2+8x−9}−\dfrac{4}{x^2+10x+9}\)
- Answer
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\(\dfrac{1}{(x−1)(x+1)}\)
62. \(\dfrac{3}{2x^2+5x+2}−\dfrac{1}{2x^2+3x+1}\)
63. \(\dfrac{5a}{a−2}+\dfrac{9}{a}−\dfrac{2a+18}{a^2−2a}\)
- Answer
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\(\dfrac{5a^2+7a−36}{a(a−2)}\)
64. \(\dfrac{2b}{b−5}+\dfrac{3}{2b}−\dfrac{2b−15}{2b^2−10b}\)
65. \(\dfrac{c}{c+2}+\dfrac{5}{c−2}−\dfrac{10c}{c^2−4}\)
- Answer
-
\(\dfrac{c−5}{c+2}\)
66. \(\dfrac{6d}{d−5}+\dfrac{1}{d+4}+\dfrac{7d−5}{d^2−d−20}\)
67. \(\dfrac{3d}{d+2}+\dfrac{4}{d}−\dfrac{d+8}{d^2+2d}\)
- Answer
-
\(\dfrac{3(d+1)}{d+2}\)
68. \(\dfrac{2q}{q+5}+\dfrac{3}{q−3}−\dfrac{13q+15}{q^2+2q−15}\)
Add and Subtract Rational Functions
In the following exercises, find a. \(R(x)=f(x)+g(x)\) b. \(R(x)=f(x)−g(x)\).
69. \(f(x)=\dfrac{−5x−5}{x^2+x−6}\) and \( g(x)=\dfrac{x+1}{2−x}\)
- Answer
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a. \(R(x)=−\dfrac{(x+8)(x+1)}{(x−2)(x+3)}\)
b. \(R(x)=\dfrac{x+1}{x+3}\)
70. \(f(x)=\dfrac{−4x−24}{x^2+x−30}\) and \( g(x)=\dfrac{x+7}{5−x}\)
71. \(f(x)=\dfrac{6x}{x^2−64}\) and \(g(x)=\dfrac{3}{x−8}\)
- Answer
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a. \(R(x)=\dfrac{3(3x+8)}{(x−8)(x+8)}\)
b. \(R(x)=\dfrac{3}{x+8}\)
72. \(f(x)=\dfrac{5}{x+7}\) and \( g(x)=\dfrac{10x}{x^2−49}\)