tớ chịu thôi SORRY CẬU RẤT NHIỀU

A=2015/2016+2016/2017+2017/2018>2015/2018+2016/2018+2017/2018

=6048/2018>1

B=2015+2016+2017/2016+2017+2018=6048/6051<1

=>A>B

Ta có \(B=\frac{2015+2016+2017}{2016+2017+2018}\)

\(\Leftrightarrow B=\frac{2015}{2016+2017+2018}+\frac{2016}{2016+2017+2018}+\frac{2017}{2016+2017+2018}\)

Vì
\(\frac{2015}{2016}>\frac{2015}{2016+2017+2018};\frac{2016}{2017}>\frac{2016}{2016+2017+2018};\frac{2017}{2018}>\frac{2017}{2016+2017+2018}\) nên \(\frac{2015}{2016}+\frac{2016}{2017}+\frac{2017}{2018}>\frac{2015}{2016+2017+2018}+\frac{2016}{2016+2017+2018}+\frac{2017}{2016+2017+2018}\)

Hay \(A>B\)

A<B(2015/2016<2015;2016/2017<2016;2017/2018<2017)

Ta có:\(Q=\frac{2015+2016+2017}{2016+2017+2018}=\frac{2015}{2016+2017+2018}+\frac{2016}{2016+2017+2018}+\frac{2017}{2016+2017+2018}\)

Vì \(\hept{\begin{cases}\frac{2015}{2016}>\frac{2015}{2016+2017+2018}\\\frac{2016}{2017}>\frac{2016}{2016+2017+2018}\\\frac{2017}{2018}>\frac{2017}{2016+2017+2018}\end{cases}}\)

\(\Rightarrow\frac{2015}{2016}+\frac{2016}{2017}+\frac{2017}{2018}>\frac{2015}{2016+2017+2018}+\frac{2016}{2016+2017+2018}+\frac{2017}{2016+2017+2018}\)

\(\Rightarrow P>Q\)

Vậy P > Q

a) Ta có: 1- 17/18= 1/18, 1- 15/16= 1/16.

Vì 1/18< 1/16 nên 17/18> 15/16.

b) Ta có: 2015/2016< 1, 2018/2017> 1 nên 2015/2016< 2018/2017.

c) 2015+ 2017/2016+ 2018= 2015+ 2017/2016+ 2018.

a)phần bù của 17/18 là:1-17/18=1/18

phần bù của 15/16 là:1-15/16=1/16

vì 1/18 <1/16 =>17/18>15/16(vì phần bù chủa p/s nào bé hơn thì số đó lớn hơn và ngược lại)

câu b làm tương tự nhé bn!

c)dấu bằng nhé

Ta có:2015/2016>2015/2016+2017+2018

2016/2017>2016/2016+2017+2018

2017/2018>2017/2016+2017+2018-Mình áp dụng so sánh phân số cùng tử đấy.

Suy ra2015/2016+2016/2017+2017/2018>(2015+2016+2017)/(2016+2017+2018)=B

\(A=\frac{2015}{2016}+\frac{2016}{2017}+\frac{2017}{2018}\)

\(B=\frac{2015+2016+2017}{2016+2017+2018}\)

\(B=\frac{2015}{2016+2017+2018}+\frac{2016}{2016+2017+2018}+\frac{2017}{2016+2017+2018}\)

Ta có:

\(\frac{2015}{2016}>\frac{2015}{2016+2017+2018}\)

\(\frac{2016}{2017}>\frac{2016}{2016+2017+2018}\)

\(\frac{2017}{2018}>\frac{2017}{2016+2017+2018}\)

Cộng vế theo vế, ta có:

\(\frac{2015}{2016}+\frac{2016}{2017}+\frac{2017}{2018}>\frac{2015}{2016+2017+2018}+\frac{2016}{2016+2017+2018}+\frac{2017}{2016+2017+2018}\)

\(hay\frac{2015}{2016}+\frac{2016}{2017}+\frac{2017}{2018}>\frac{2015+2016+2017}{2016+2017+2018}\)

\(\Rightarrow A>B\)

Vậy A >  B

Đặt 2015.2016+2016=n

suy ra A=(n+1)/n   và B=(n+2)/(n+1)

Ta có A - B=(n+1)/n -(n+2)/(n+1)=((n+1)²-n(n+2))/n(n+1)=(n²+2n+1-n²-2n)/n(n+1)=1/n(n+1)

Vì A-B lớn hơn 0 nên A>B

thanks