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20 tháng 6 2017

\(\left(\frac{3}{2}+\frac{1}{3}-\frac{2}{5}\right)-\left(\frac{1}{2}-\frac{2}{3}+\frac{3}{5}\right)\)

\(=\frac{3}{2}+\frac{1}{3}-\frac{2}{5}-\frac{1}{2}+\frac{2}{3}-\frac{3}{5}\)

\(=\frac{3}{2}-\frac{1}{2}+\frac{1}{3}+\frac{2}{3}-\frac{2}{5}-\frac{3}{5}\)

\(=1+1-1=1\)

(32 +13 −25 )−(12 −23 +35 )

=32 +13 −25 −12 +23 −35 

=32 −12 +13 +23 −25 −35 

=1+1−1=1

k nha

HQ
Hà Quang Minh
Giáo viên
8 tháng 10 2023

(A) \(\frac{2}{3} + \frac{{ - 4}}{6} = \frac{4}{6} + \frac{{ - 4}}{6} = 0\) => A sai

(B) \(\frac{2}{3}.\frac{{ - 1}}{5} = \frac{{ - 2}}{{15}}\) mà \(\frac{{3 - 2}}{5} = \frac{1}{5}\) => B sai

(C) \(\frac{2}{3} - \frac{3}{5} = \frac{{10}}{{15}} - \frac{9}{{15}} = \frac{1}{{15}}\) => C đúng

(D) \(\frac{3}{5}:\frac{3}{{ - 5}} = \frac{3}{5}.\frac{{ - 5}}{3} = \frac{{ - 15}}{{15}} =  - 1\) => D sai

=> Chọn C.

2 tháng 4 2023

1+1=3 :)))

11 tháng 6 2016

Đặt A = 1/2 - 1/3 - 2/3 + 1/4 + 2/4 + 3/4 - 1/5 - 2/5 - 3/5 - 4/5 + ... + 1/10 + ...+ 9/10

A = 1/2 - ( 1/3 + 2/3) + (1/4 + 2/4 + 3/4) - ( 1/5 + 2/5 + 3/5 + 4/5) + ( 1/6 + 2/6 + ...  + 5/6) - ( 1/7 + 2/7 + ... + 6/7) + ( 1/8 + 2/8 + ... + 7/8) - ( 1/9 + 2/9 + ... + 8/9)

A = 1/2 - 1 + [( 1/4 + 3/4) + 2/4] - [(1/5 + 4/5) + (2/5 + 3/5)] + [(1/6+5/6) + ( 2/6 + 4/6) + 3/6] - [(1/7 + 6/7) + (2/7 + 5/7) + (3/7 + 4/7)] + [(1/8 + 7/8) + (2/8 + 6/8) + (3/8 + 5/8) + 4/8)] - [(1/9 + 8/9) + (2/9 + 7/9) + (3/9 + 6/9) + (4/9 + 5/9)] + [(1/10 + 9/10) + ( 2/10 + 8/10) + ( 3/10 + 7/10) + ( 4/10 + 6/10) + 5/10]

A = 1/2 - 1 + ( 1 + 1/2) - 2 + ( 2 + 1/2) - 3 + ( 3 + 1/2) - 4 + ( 4 + 1/2) 

A = 1/2 + 1/2 + 1/2 + 1/2 + 1/2 

A = 1/2 × 5 = 5/2

15 tháng 6 2016

Đặt A = 1/2 - 1/3 - 2/3 + 1/4 + 2/4 + 3/4 - 1/5 - 2/5 - 3/5 - 4/5 + ... + 1/10 + ...+ 9/10

A = 1/2 - ( 1/3 + 2/3) + (1/4 + 2/4 + 3/4) - ( 1/5 + 2/5 + 3/5 + 4/5) + ( 1/6 + 2/6 + ...  + 5/6) - ( 1/7 + 2/7 + ... + 6/7) + ( 1/8 + 2/8 + ... + 7/8) - ( 1/9 + 2/9 + ... + 8/9)

A = 1/2 - 1 + [( 1/4 + 3/4) + 2/4] - [(1/5 + 4/5) + (2/5 + 3/5)] + [(1/6+5/6) + ( 2/6 + 4/6) + 3/6] - [(1/7 + 6/7) + (2/7 + 5/7) + (3/7 + 4/7)] + [(1/8 + 7/8) + (2/8 + 6/8) + (3/8 + 5/8) + 4/8)] - [(1/9 + 8/9) + (2/9 + 7/9) + (3/9 + 6/9) + (4/9 + 5/9)] + [(1/10 + 9/10) + ( 2/10 + 8/10) + ( 3/10 + 7/10) + ( 4/10 + 6/10) + 5/10]

A = 1/2 - 1 + ( 1 + 1/2) - 2 + ( 2 + 1/2) - 3 + ( 3 + 1/2) - 4 + ( 4 + 1/2) 

A = 1/2 + 1/2 + 1/2 + 1/2 + 1/2 

A = 1/2 × 5 = 5/2

25 tháng 8 2016

\(\frac{\frac{2}{5}+\frac{2}{7}-\frac{2}{11}}{\frac{3}{5}+\frac{3}{7}-\frac{3}{11}}+\frac{\frac{1}{4}-\frac{1}{5}+\frac{1}{7}}{\frac{3}{4}-\frac{3}{5}+\frac{3}{7}}\)

\(=\frac{2\left(\frac{1}{5}+\frac{1}{7}-\frac{1}{11}\right)}{3\left(\frac{1}{5}+\frac{1}{7}-\frac{1}{11}\right)}+\frac{1\left(\frac{1}{4}-\frac{1}{5}+\frac{1}{7}\right)}{3\left(\frac{1}{4}-\frac{1}{5}+\frac{1}{7}\right)}\)

\(=\frac{2}{3}+\frac{1}{3}\)

\(=1\)

17 tháng 9 2016

\(\frac{1}{2}-\frac{2}{3}+\frac{3}{4}-\frac{4}{5}-\frac{6}{7}-\frac{5}{6}+\frac{4}{5}-\frac{3}{4}+\frac{2}{3}-\frac{1}{2}\)

\(=\left(\frac{1}{2}-\frac{1}{2}\right)-\left(\frac{2}{3}-\frac{2}{3}\right)+\left(\frac{3}{4}-\frac{3}{4}\right)-\left(\frac{4}{5}-\frac{4}{5}\right)-\left(\frac{6}{7}+\frac{5}{6}\right)\)

\(=-\frac{71}{42}\)

17 tháng 9 2016

71/42

26 tháng 3 2017

(2/5+2/7-2/11):(3/7-3/11+3/5) =2/5+2/7-2/11.7/3-11/3+5/3=2/1+2/1-2/1.1/3-1/3+1/3=2+1/3=7/3                                                                          Em đây mới học lớp 6 nên hay xem kĩ lại và tính bang máy tính  

16 tháng 4 2017

a, 2/3

b,1

nhớ nhé

16 tháng 8 2016

\(\left(\frac{3}{5}-\frac{1}{2}+\frac{7}{3}\right)-\left(\frac{1}{3}-\frac{5}{2}+\frac{1}{5}\right)-\left(-\frac{3}{5}+3-\frac{5}{3}\right)\)

\(=\frac{3}{5}-\frac{1}{2}+\frac{7}{3}-\frac{1}{3}+\frac{5}{2}-\frac{1}{5}+\frac{3}{5}-3+\frac{5}{3}\)

\(=\frac{3}{5}+\frac{-1}{2}+\frac{7}{3}+\frac{-1}{3}+\frac{5}{2}+\frac{-1}{5}+\frac{3}{5}+\left(-3\right)+\frac{5}{3}\)

\(=\left(\frac{3}{5}+\frac{-1}{5}+\frac{3}{5}\right)+\left(\frac{-1}{2}+\frac{5}{2}\right)+\left(\frac{7}{3}+\frac{-1}{3}+\frac{5}{3}\right)+\left(-3\right)\)

\(=\frac{5}{2}+\frac{4}{2}+\frac{11}{3}+\left(-3\right)\)

\(=1+2+\frac{11}{3}+\left(-3\right)\)

\(=0+\frac{11}{3}\)

\(=\frac{11}{3}\)

16 tháng 8 2016

\(\left(\frac{3}{5}-\frac{1}{2}+\frac{7}{3}\right)-\left(\frac{1}{3}-\frac{5}{2}+\frac{1}{5}\right)-\left(-\frac{3}{5}+3-\frac{5}{3}\right)\)

\(=\frac{3}{5}-\frac{1}{2}+\frac{7}{3}-\frac{1}{3}+\frac{5}{2}-\frac{1}{5}+\frac{3}{5}-3+\frac{5}{3}\)

\(=\left(\frac{3}{5}-\frac{1}{5}+\frac{3}{5}\right)+\left(-\frac{1}{2}+\frac{5}{2}\right)+\left(\frac{7}{3}-\frac{1}{3}+\frac{5}{3}\right)-3\)

\(=1+2+\frac{11}{3}-3\)

\(=\left(1+2-3\right)+\frac{11}{3}\)

\(=0+\frac{11}{3}\)

=\(\frac{11}{3}\)

(Bài làm có gì ko hiểu bn cứ hỏi mk nhé hihi ^...^ ^_^)