a) \(\frac{8}{21}+\frac{13}{21}=\frac{8+13}{21}=\frac{21}{21}=1\)

b) \(\frac{5}{6}:\frac{-7}{12}=\frac{5}{6}.\frac{12}{-7}=\frac{10}{-7}\)

c) \(-4\frac{1}{4}-\frac{3}{4}=\frac{-17}{4}-\frac{3}{4}=\frac{-17-3}{4}=\frac{-20}{4}=-5\)

d) \(\frac{7}{9}.\frac{8}{17}+\frac{7}{9}.\frac{15}{17}-\frac{7}{9}.\frac{6}{17}\)

\(=\frac{7}{9}.\left(\frac{8}{17}+\frac{15}{17}-\frac{6}{17}\right)\)

\(=\frac{7}{9}.\frac{17}{17}\)

\(=\frac{7}{9}.1\)

\(=\frac{7}{9}\)

a) \(\frac{8}{21}+\frac{13}{21}=1\)

b) \(\frac{5}{6}\div\frac{-7}{12}=\frac{5}{6}.\frac{-12}{7}=\frac{-10}{7}\)

c) \(-4\frac{1}{4}-\frac{3}{4}=\frac{-17}{4}-\frac{3}{4}=-5\)

d) \(\frac{7}{9}.\frac{8}{17}+\frac{7}{9}.\frac{15}{7}-\frac{7}{9}.\frac{6}{17}=\frac{7}{9}.\left(\frac{8}{17}+\frac{15}{17}-\frac{6}{17}\right)=\frac{7}{9}.1=\frac{7}{9}\)

1.những số bé hơn 3 là:1,2

Vay x là: 1,2

1.a) x\(\in\)-1;1;-2;2;0

2.a) = -1600

   b) = 168

   c) = -567

tính thôi hả bạn

bằng 5,4!!

Hết 85h

Bố Bình đi làm hết 85 giờ

Cho s= 2010/2011+2011/2012+2012/2013/2013/2010

Cho s=1

AM-GM:\(\frac{2010}{2011}+\frac{2011}{2012}+\frac{2012}{2013}+\frac{2013}{2010}\ge4\sqrt[4]{\frac{2010.2011.2012.2013}{2011.2012.2013.2010}}=4\sqrt[4]{1}=4\)

\(\Rightarrow S\ge4\)

^^

x = -213 nha bạn 

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 \(A>B\)