a) \(22\frac{1}{2}\cdot\frac{7}{9}+50\%-1,25\)

\(=\frac{45}{2}\cdot\frac{7}{9}+\frac{50}{100}-\frac{125}{100}\)

\(=\frac{5}{2}\cdot\frac{7}{1}+\frac{1}{2}-\frac{5}{4}\)

\(=\frac{35}{2}+\frac{1}{2}-\frac{5}{4}=18-\frac{5}{4}=\frac{67}{4}\)

b) \(1,4\cdot\frac{15}{49}-\left(\frac{4}{5}+\frac{2}{3}\right):2\frac{1}{5}\)

\(=\frac{7}{5}\cdot\frac{15}{49}-\frac{22}{15}:\frac{11}{15}\)

\(=\frac{1}{1}\cdot\frac{3}{7}-\frac{22}{15}\cdot\frac{15}{11}\)

\(=\frac{3}{7}-2=\frac{3-14}{7}=\frac{-11}{7}\)

c) \(\left(-\frac{1}{2}\right)^2-\frac{7}{16}:\frac{7}{4}+75\%\)

\(=\frac{1}{4}-\frac{7}{16}\cdot\frac{4}{7}+\frac{75}{100}\)

\(=\frac{1}{4}-\frac{1}{4}+\frac{3}{4}=\frac{3}{4}\)

Bài 2  Bạn tự làm nhé

1.a,\(22\frac{1}{2}.\frac{7}{9}+50\%-1,25\)

\(=\frac{45}{2}.\frac{7}{9}+\frac{1}{2}-\frac{5}{4}\)

\(=\frac{35}{2}+\frac{1}{2}-\frac{5}{4}\)

\(=\frac{67}{4}\)

b,Các phép tính khác làm tương tự

Đổi các số ra hết thành phân số,có ngoặc thì lm ngoặc trc,Xoq đến nhân chia trước dồi mới cộng trừ

c,tương tự

2.

a,\(1\frac{3}{5}+\frac{7}{12}\div x=\frac{-9}{4}\)

\(\frac{8}{5}+\frac{7}{12}\div x=\frac{-9}{4}\)

\(\frac{7}{12}\div x=\frac{-77}{20}\)

Đến đây dễ bạn tự làm

b,\(\left(2\frac{4}{5}.x+50\right)\div\frac{2}{3}=-51\)

\(\left(\frac{14}{5}x+50\right)\div\frac{2}{3}=-51\)

\(\frac{14}{5}x+50=-34\)

\(\frac{14}{5}x=-84\)

Tự làm tiếp

c,\(\left|\frac{3}{4}.x-\frac{1}{2}\right|=\frac{1}{4}\)\(\Rightarrow\left|\frac{3}{4}x-\frac{1}{2}\right|=\varnothing\)

\(a,\frac{3}{4}.\left(x+2\right)+\frac{1}{2}.\left(x-\frac{1}{2}\right)=\frac{15}{4}\)

\(\frac{3}{4}.x+\frac{3}{4}.2+\frac{1}{2}.x+\frac{1}{2}.\left(-\frac{1}{2}\right)=\frac{15}{4}\)

\(\left(\frac{3}{4}.x+\frac{1}{2}.x\right)+\frac{3}{2}-\frac{1}{4}=\frac{15}{4}\)

\(\left(\frac{3}{4}+\frac{1}{3}\right).x=\frac{15}{4}+\frac{1}{4}-\frac{3}{2}\)

\(\frac{5}{4}.x=\frac{5}{2}\)

\(x=\frac{5}{2}:\frac{5}{4}\)

\(x=2\)

\(b,3.x-\frac{3}{5}=0\)

\(3.x=0+\frac{3}{5}\)

\(3.x=\frac{3}{5}\)

\(x=\frac{3}{5}:3\)

\(x=\frac{1}{5}\)

\(c,\frac{-2}{3}.x-\frac{1}{3}.\left(2.x-3\right)=\frac{3}{2}\)

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

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

\(-\frac{4}{3}.x=\frac{1}{2}\)

\(x=\frac{1}{2}:\left(\frac{-4}{3}\right)\)

\(x=\frac{-3}{8}\)

Học tốt

Ta có : \(A=\frac{1}{2^2}+\frac{1}{3^2}+\frac{1}{4^2}+...+\frac{1}{2015^2}=\frac{1}{2.2}+\frac{1}{3.3}+\frac{1}{4.4}+...+\frac{1}{2015.2015}\) 

\(< \frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{2014.2015}=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{2014}-\frac{1}{2015}\)

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

=> A < 1 (đpcm)

a) 4/ 3x7 + 4/7x11+ 4/11x15+...+ 4/107x111

=1/3-1/7+ 1/7-1/11+ 1/11- 1/15+...+1/107 - 1/111

= 1/3-1/111

=12/37

\(b,\frac{3^2}{8\cdot11}+\frac{3^2}{11\cdot14}+\frac{3^2}{14\cdot17}+...+\frac{3^2}{197\cdot200}\)

\(=3\left(\frac{3}{8\cdot11}+\frac{3}{11\cdot14}+\frac{3}{14\cdot17}+...+\frac{3}{197\cdot200}\right)\)

\(=3\left(\frac{1}{8}-\frac{1}{11}+\frac{1}{11}-\frac{1}{14}+\frac{1}{14}-\frac{1}{17}+...+\frac{1}{197}-\frac{1}{200}\right)\)

\(=3\left(\frac{1}{8}-\frac{1}{200}\right)\)

\(=3\cdot\frac{3}{25}=\frac{9}{25}\)

a) \(\frac{1}{3}-\frac{-1}{6}=\frac{1}{3}+\frac{1}{6}=\frac{1}{2}\)

b) \(2\frac{1}{3}+4\frac{1}{5}=\frac{7}{3}+\frac{21}{5}=\frac{98}{15}\)

c) \(\frac{4}{9}-\frac{13}{3}-\frac{4}{9}-\frac{10}{3}=\left(\frac{4}{9}-\frac{4}{9}\right)-\left(\frac{13}{3}+\frac{10}{3}\right)\)

\(=0-\frac{23}{3}=\frac{-23}{3}\)

d) \(4-\left(2-\frac{5}{2}\right)+0,5=4-2+\frac{5}{2}+\frac{1}{2}=2+3=5\)

à có,à ko

hihi nói xạo đó.

thằng phạm thị cẩm tú kia ngứa mồm à 

như thằng dở ý 

làm hộ tôi được thì không thì thôi ok 

a,-3/5.2/7+-3/7.3/5+-3/7

=-3/7.2/5+(-3/7).3/5+(-3/7) 

=-3/7(2/5+3/5+1)

=-3/7.2

=-6/7

\(a,\left(4\frac{1}{2}-\frac{2}{5}x\right):1\frac{3}{4}=\frac{11}{14}\)

\(\Rightarrow\left(\frac{9}{2}-\frac{2}{5}x\right):\frac{7}{4}=\frac{11}{4}\)

\(\Rightarrow\left(\frac{9}{2}-\frac{2}{5}x\right)=\frac{11}{4}\cdot\frac{7}{4}\)

\(\Rightarrow\left(\frac{9}{2}-\frac{2}{5}x\right)=\frac{77}{16}\)

\(\Rightarrow\frac{9}{2}-\frac{2}{5}x=\frac{77}{16}\)

\(\Rightarrow-\frac{2}{5}x=\frac{77}{16}-\frac{9}{2}\)

\(\Rightarrow-\frac{2}{5}x=\frac{5}{16}\)

\(\Rightarrow x=\frac{5}{16}:\left(-\frac{2}{5}\right)\)

\(\Rightarrow x=-\frac{25}{32}\)

\(b,\frac{2}{3}\cdot x-\frac{2}{5}x=\frac{9}{3}\)

\(\Rightarrow x\left(\frac{2}{3}-\frac{2}{5}\right)=\frac{8}{3}\)

\(\Rightarrow x\cdot\frac{4}{15}=\frac{8}{3}\)

\(\Rightarrow x=\frac{8}{3}:\frac{4}{15}\)

\(\Rightarrow x=10\)

\(c,\frac{-2}{3}|x|+1\frac{1}{2}=\frac{2}{5}\)

\(\Rightarrow\frac{-2}{3}|x|+\frac{3}{2}=\frac{2}{5}\)

\(\Rightarrow\frac{-2}{3}|x|=\frac{2}{5}-\frac{3}{2}\)

\(\Rightarrow\frac{-2}{3}|x|=-\frac{11}{10}\)

\(\Rightarrow|x|=\frac{-11}{10}:\frac{-2}{3}\)

\(\Rightarrow|x|=\frac{33}{20}\)

\(\Rightarrow\orbr{\begin{cases}x=\frac{33}{20}\\x=-\frac{33}{20}\end{cases}}\)

\(d,|2x-\frac{1}{3}|+\frac{1}{6}=\frac{3}{4}\)

\(\Rightarrow|2x-\frac{1}{3}|=\frac{3}{4}-\frac{1}{6}\)

\(\Rightarrow|2x-\frac{1}{3}|=\frac{7}{12}\)

\(\Rightarrow\orbr{\begin{cases}2x-\frac{1}{3}=\frac{7}{12}\\2x-\frac{1}{3}=-\frac{7}{12}\end{cases}\Rightarrow\orbr{\begin{cases}2x=\frac{11}{12}\\2x=-\frac{1}{4}\end{cases}}\Rightarrow\orbr{\begin{cases}x=\frac{11}{24}\\x=-\frac{1}{8}\end{cases}}}\)