6,8 %=0,068 bạn nhé

680/100

tử của M=[(1/99)+(99/1)]x99/2=480298/99                tương tự mẫuM=1173/50

tử N=[22513/450]                                                                  mẫu N=9919/1800

sao bấm ra số ảo quá. tính tỉ số tự tính đi.

cậu có xem noob team ko

\(A=\frac{1}{2^2}+\frac{1}{3^2}+...+\frac{1}{10^2}\)

\(< \frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{9.10}\)

\(=\frac{2-1}{1.2}+\frac{3-2}{2.3}+...+\frac{10-9}{9.10}\)

\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{9}-\frac{1}{10}=\frac{9}{10}\)

15-2x=25

2x=15-25

2x=-10

x=-10:2

x=-5

31-(17+x)=18

17+x=31-18

17+x=13

x=13-17

x=-4

15 - 2.x = 25

2. x = 15 - 25

2 . x =  -10

x = -10 : 2

x = -5

31 - ( 17 + x ) = 18 

17 + x = 31- 18

17 + x = 13

x = 17 - 13

x = 4

\(A=\frac{4}{1.2}+\frac{4}{2.3}+\frac{4}{3.4}+...+\frac{4}{2014.2015}\)

\(=4\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{2014.2015}\right)\)

\(=4\left(\frac{2-1}{1.2}+\frac{3-2}{2.3}+...+\frac{2015-2014}{2014.2015}\right)\)

\(=4\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{2014}-\frac{1}{2015}\right)\)

\(=4\left(1-\frac{1}{2015}\right)=\frac{8056}{2015}\)

`Answer:`

\(\left(\frac{3}{10}-x\right)-\frac{1}{3}=-\frac{2}{5}\)

\(\Leftrightarrow\frac{3}{10}-x=-\frac{2}{5}:-\frac{1}{3}\)

\(\Leftrightarrow\frac{3}{10}-x=\frac{6}{5}\)

\(\Leftrightarrow x=\frac{3}{10}-\frac{6}{5}\)

\(\Leftrightarrow x=-\frac{9}{10}\)

\(\frac{7}{9}-\frac{2}{9}x=\frac{4}{3}\)

\(\Leftrightarrow\frac{2}{9}x=\frac{7}{9}-\frac{4}{3}\)

\(\Leftrightarrow\frac{2}{9}x=-\frac{5}{9}\)

\(\Leftrightarrow x=-\frac{5}{9}:\frac{2}{9}\)

\(\Leftrightarrow x=-\frac{5}{2}\)

\(\frac{1}{3}+\frac{2}{3}:x=-7\)

\(\Leftrightarrow\frac{2}{3}:x=-7-\frac{1}{3}\)

\(\Leftrightarrow\frac{2}{3}:x=-\frac{22}{3}\)

\(\Leftrightarrow x=-\frac{22}{3}.\frac{2}{3}\)

\(\Leftrightarrow x=-\frac{44}{9}\)