a. Tìm n ∈ Z sao cho A= $\frac{2}{n+1}$ ∈ Z b. Tìm n ∈ Z sao cho B= $\frac{3}{n-2}$ ∈ Z c. Tìm n ∈ Z sao cho C= $\frac{3}{n+2}$ ∈ Z d. Tìm n ∈ Z sao cho D= $\frac{n}{n-1}$ ∈ Z e. Tìm n ∈ Z sao cho E= $\frac{n}{n+1}$ ∈ Z

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