Tạm thời chỉ nghĩ ra được cách này -_- 

Ta có : 

\(A=\frac{2014}{2015}+\frac{2015}{2016}+\frac{2016}{2014}\)

\(A=\frac{2015-1}{2015}+\frac{2016-1}{2016}+\frac{2014+2}{2014}\)

\(A=\frac{2015}{2015}-\frac{1}{2015}+\frac{2016}{2016}-\frac{1}{2016}+\frac{2014}{2014}+\frac{2}{2014}\)

\(A=1-\frac{1}{2015}+1-\frac{1}{2016}+1+\frac{2}{2014}\)

\(A=\left(1+1+1\right)-\left(\frac{1}{2015}+\frac{1}{2016}-\frac{2}{2014}\right)\)

\(A=3-\left[\left(\frac{1}{2015}+\frac{1}{2016}\right)-\left(\frac{1}{2014}+\frac{1}{2014}\right)\right]\)

Lại có : 

\(\frac{1}{2015}< \frac{1}{2014}\)

\(\frac{1}{2016}< \frac{1}{2014}\)

\(\Rightarrow\)\(\frac{1}{2015}+\frac{1}{2016}< \frac{1}{2014}+\frac{1}{2014}\)

\(\Rightarrow\)\(\left(\frac{1}{2015}+\frac{1}{2016}\right)-\left(\frac{1}{2014}+\frac{1}{2014}\right)< 0\)

\(\Rightarrow\)\(A=3-\left[\left(\frac{1}{2015}+\frac{1}{2016}\right)-\left(\frac{1}{2014}+\frac{1}{2014}\right)\right]>3\)

Vậy \(A>3\)

Chúc bạn học tốt ~ 

ta có 2015/2016+2016/2017+2017/2015=(1-1/2016)+(1-1/2017)+(2+1/2015)

                                                         =4-(1/2016+1/2017-1/2015)

                   1/2016<1; 1/2017<1 nên 1/2016+1/2017<2 suy ra 1/2016+1/2017-1/2015<1(vì 1/2015<1)

4-(1/2016+1/2017-1/2015)>4-1=3           

2015/2016+2016/2017+2017/2015>3

cho mik nhé                       

A = (n + 2015)(n + 2016) + n² + n

= (n + 2015)(n + 2015 + 1) + n(n + 1)

Tích 2 số tự nhiên liên tiếp luôn chia hết cho 2

=> (n + 2015)(n + 2015 + 1) chia hết cho 2

      n(n + 1) chia hết cho 2

=> (n + 2015)(n + 2015 + 1) + n(n + 1) chia hết cho 2

=> A chia hết cho 2 với mọi n \(\in\) N (đpcm)

\(\frac{2015}{2016}+\frac{2016}{2017}>\frac{\left(2015+2016\right)}{\left(2016+2017\right)}=\frac{2015}{2016+2017}+\frac{2016}{2016+2017}\)

ko bit

(2016/2017) = (2017/2016)

\(A=\frac{2015}{2016}+\frac{2016}{2017}=1-\frac{1}{2016}+1-\frac{1}{2017}>1\)

\(B=\frac{2015+2016}{2016+2017}< \frac{2016+2017}{2016+2017}=1\)

Suy ra \(A>B\).

có cách nhanh hơn

\(A=\frac{2015}{2016}+\frac{2016}{2017}\)   

\(=1-\frac{1}{2015}+1-\frac{1}{2016}\)    

\(=2-\left(\frac{1}{2015}+\frac{1}{2016}\right)>1\)   

\(B=\frac{2015+2016}{2016+2017}\)   

\(=\frac{4031}{4033}\)   

\(=1-\frac{2}{4033}< 1\)

Vậy A > B 

A-3=2014/2015+2015/2016+2017/2015-3

=>A-3=-1/2015-1/2016+2/2015

=>A-3=1/2015-1/2016

Vì 1/2015>1/2016

=>1/2015-1/2016>0

=>A-3>0

=>A>3