Quy đồng

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Bài 1: Quy đồng

a. $1 - \frac{1}{x+1} + \frac{1}{x^3+1}$

b. $\frac{x^2+2}{x^3-1} + \frac{2}{x^2-x+1} + \frac{1}{1-x}$

c. $\frac{x^3 + 2x + 2}{x^3+1} + \frac{2x + 1}{x^2+x+1} + \frac{1}{x+1}$

d. $4 - \frac{3xy}{x-y} + \frac{x-y}{x^3-y^3}$

e. $\frac{1}{x-y} + \frac{3xy}{y^3+x^3} + \frac{x-y}{x^2+xy+y^2}$