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\(a,\frac{1}{2\times3}+\frac{1}{3\times4}+\frac{1}{4\times5}+\frac{1}{5\times6}=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}\)
\(=\frac{1}{2}-\frac{1}{6}=\frac{1}{3}\)
\(b,\left(1-\frac{1}{2}\right)\times\left(1-\frac{1}{3}\right)\times\left(1-\frac{1}{4}\right)=\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\)
\(=\frac{1\times2\times3}{2\times3\times4}=\frac{1}{4}\)
1-(1-(1/2 × 3/5 + 1/5 × 1/2 + 2/10 × 1/2 +1/2)
=1-(1-(3/10 + 1/10 + 1/10 + 5/10)
=1-(1-(3+1+1+5/10)
=1-(1- 10/10)
=1-(1-1)
=1-0
=1
\(1-\left[1-\left(\frac{1}{2}\times\frac{3}{5}+\frac{1}{5}\times\frac{1}{2}+\frac{2}{10}\times\frac{1}{2}+\frac{1}{2}\right)\right]\)
\(=1-\left[1-\left\{\frac{1}{2}\times\left(\frac{3}{5}+\frac{1}{5}+\frac{2}{10}+\frac{1}{2}\right)\right\}\right]\)
\(=1-\left[1-\left\{\frac{1}{2}\times\left(\frac{6}{10}+\frac{2}{10}+\frac{2}{10}+\frac{5}{10}\right)\right\}\right]\)
\(=1-\left[1-\left\{\frac{1}{2}\times\left(\frac{6+2+2+5}{10}\right)\right\}\right]\)
\(=1-\left[1-\left\{\frac{1}{2}\times\frac{3}{2}\right\}\right]\)
\(=1-\left[1-\frac{3}{4}\right]\)
\(=1-\frac{1}{4}\)
\(=\frac{3}{4}\)
bài 1:
\(\frac{6}{11}+\frac{1}{3}+\frac{5}{11}\)
\(=\left(\frac{6}{11}+\frac{5}{11}\right)+\frac{1}{3}\)
\(=\frac{11}{11}+\frac{1}{3}=1+\frac{1}{3}=\frac{3}{3}+\frac{1}{3}=\frac{4}{3}\)
bài 2:
\(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}\)
\(=\left(\frac{1}{2}+\frac{1}{20}\right)+\left(\frac{1}{6}+\frac{1}{12}\right)\)
\(=\frac{11}{20}+\frac{1}{4}=\frac{11}{20}+\frac{5}{20}=\frac{15}{20}=\frac{3}{4}\)
bài 3:
a) \(\frac{3}{2}\cdot\frac{4}{5}\cdot\frac{2}{3}=\left(\frac{3}{2}\cdot\frac{2}{3}\right)\cdot\frac{4}{5}=1\cdot\frac{4}{5}=\frac{4}{5}\)
b) \(\frac{6}{7}\cdot\frac{5}{3}\cdot\frac{7}{6}=\left(\frac{6}{7}\cdot\frac{7}{6}\right)\cdot\frac{5}{3}=1\cdot\frac{5}{3}=\frac{5}{3}\)
bài 4:
a) \(\frac{2}{5}\cdot\frac{1}{4}+\frac{3}{4}\cdot\frac{2}{5}=\frac{2}{5}\cdot\left(\frac{1}{4}+\frac{3}{4}\right)=\frac{2}{5}\cdot1=\frac{2}{5}\)
b) \(\frac{6}{11}:\frac{2}{3}+\frac{5}{11}:\frac{2}{3}=\left(\frac{6}{11}+\frac{5}{11}\right):\frac{2}{3}=1:\frac{2}{3}=\frac{3}{2}\)
Bài 1:
6/11 + 1/3 + 5/11
= ( 6/11 + 5/11) + 1/3
= 11/11 + 1/3
= 1 + 1/3
= 3/3 +1/3
= 4/3
Bài 2:
1/2 + 1/6 + 1/12 + 1/20
= ( 1/2 + 1/6 + 1/12 ) + 1/20
= ( 6/12 + 2/12 + 1/12 ) + 1/20
=9/12 + 1/20
= 3/4 +1/20
= 15/20 + 1/20
= 16/20 = 4/5
Bài 3:
a) \(\frac{3}{2}\times\frac{4}{5}\times\frac{2}{3}\) \(=\left(\frac{3}{2}\times\frac{2}{3}\right)\times\frac{4}{5}\)\(=1\times\frac{4}{5}=\frac{4}{5}\)
b) \(\frac{6}{7}\times\left(\frac{5}{3}\times\frac{7}{6}\right)\) \(=\frac{6}{7}\times\frac{35}{18}\)\(=\frac{1\times5}{7\times3}=\frac{5}{21}\)
Bài 4:
a) 2/5 x 1/4 + 3/4 x 2/5
= 2/5 x ( 1/4 + 3/4)
= 2/5 x 1
= 2/5
b) 6/11 : 2/3 +5/11 : 2/3
= ( 6/11 + 5/11) x 3/2
= 11/11 x 3/2
= 1 x 3/2
= 3/2
....
\(\left(\frac{1}{3}-\frac{1}{5}\right)\times\frac{1}{2}=\frac{1}{6}-\frac{1}{10}\)
\(=\frac{1}{15}\)
\(\left(\frac{1}{3}-\frac{1}{5}\right)\times\frac{1}{2}=\frac{2}{15}\times\frac{1}{2}=\frac{1}{15}\)
a) $\frac{1}{6} + \frac{3}{2} + \frac{1}{2} = \frac{1}{6} + \left( {\frac{3}{2} + \frac{1}{2}} \right) = \frac{1}{6} + \frac{4}{2} = \frac{1}{6} + \frac{{12}}{6} = \frac{{13}}{6}$
b) $\frac{3}{8} + \frac{1}{2} + \frac{1}{8} = \left( {\frac{3}{8} + \frac{1}{8}} \right) + \frac{1}{2} = \frac{1}{2} + \frac{1}{2} = \frac{2}{2} = 1$
c) $\frac{2}{5} + \frac{6}{{10}} + \frac{3}{5} = \frac{2}{5} + \frac{3}{5} + \frac{3}{5} = \frac{{2 + 3 + 3}}{5} = \frac{8}{5}$
Bài 1 :
A = 1 - 1/2 + 1/2 - 1/4 + 1/4 - 1/8 + 1/8 - 1/16 + ... + 1/32 - 1/64
A = 1 - 1/64
A = 63/64
Ta có: 272727x28 - 282828x27 = 27x10101x28 - 28x10101x27 = 0
Vậy, phép tính đã cho bằng 0
4) \(\frac{29x101-101}{2x19x101+4x101}\)
= \(\frac{\left(29-1\right)x101}{\left(38-4\right)x101}\)
=\(\frac{28}{34}=\frac{14}{17}\)
5) \(\left(\frac{2}{7}+\frac{11}{7}+\frac{1}{7}\right)-\frac{3}{8}-\frac{5}{8}+\frac{1}{3}\)
= \(\frac{14}{7}-\frac{8}{8}+\frac{1}{3}\)
= \(2-1+\frac{1}{3}=\frac{4}{3}\)
Nhớ tk cho mình nhé
1\(\frac{423133x846267+423134}{423133x846267+423134}=1\))
\(\frac{\left(423133+1\right)x846267-423133}{423133x846267+423134}\)
=\(\frac{423133x846267+846267-423133}{423133x846267+423134}\)
= \(\frac{423133x846267+423134}{423133x846267+423134}\)
= 1
Nhớ tk cho mình nhé (các câu sau làm riêng cho đỡ dài
=> x + 1/2 = 5/6 + 3/4
=> x + 1/2 = 19/12
=> x = 19/12 - 1/2
=> x = 13/12
Vậy x = 13/12
Tk mk nha
a X+1/2-3/4=5/6 suy ra : Mỉnh phải đi ngủ rồi mai mình giải tiếp cho nhé
X+1/2=5/6+3/4
X+1/2=19/12
X=19/12-1/2
X=13/12
a, \(\frac{2}{3}+\frac{2}{3}+\frac{6}{3}=\frac{10}{3}\)
b,\(\frac{3}{4}+\frac{3}{4}+\frac{3}{2}=\frac{6}{4}+\frac{3}{2}=\frac{3}{2}+\frac{3}{2}=\frac{6}{2}=3\)
a) Cách 1 : \(\left(\frac{1}{3}+\frac{1}{5}\right)\times2=\left(\frac{5}{15}+\frac{3}{15}\right)\times2=\frac{8}{15}\times2=\frac{16}{15}\)
Cách 2 : \(\left(\frac{1}{3}+\frac{1}{5}\right)\times2=\frac{1}{3}\times2+\frac{1}{5}\times2=\frac{2}{3}+\frac{2}{5}=\frac{10}{15}+\frac{6}{15}=\frac{16}{15}\)
b) Cách 1 : \(\left(\frac{1}{3}-\frac{1}{5}\right)\times2=\left(\frac{5}{15}-\frac{3}{15}\right)\times2=\frac{2}{15}\times2=\frac{4}{15}\)
Cách 2 : \(\left(\frac{1}{3}-\frac{1}{5}\right)\times2=\frac{1}{3}\times2-\frac{1}{5}\times2=\frac{2}{3}-\frac{2}{5}=\frac{10-6}{15}=\frac{4}{15}\)
giỏi thế cậu ơi!!