1/1x2 + 1/2x3+ 1/3x4+....+1/2009x2010

= 1/1-1/2 + 1/2-1/3+ 1/3-1/4+...+1/2009-1/2010

= 1/1-1/2010

= 2009/2010

\(\frac{1}{1\cdot2}+\cdot\cdot\cdot+\frac{1}{2009\cdot2010}\)

\(=1-\frac{1}{2}+\cdot\cdot\cdot+\frac{1}{2009}-\frac{1}{2010}\)

\(=1-\frac{1}{2010}\)

\(=\frac{2009}{2010}\)

2/ 3x5+ 2/5x7+ 2/7x9+...+2/2007x2011+ 2/2011x2013

= 1/3-1/5+ 1/5-1/7+ 1/7-1/9+...+1/2007-1/2011+ 1/2011- 1/2013

= 1/3-1/2013

= 670/2013

64.4+18.4+9.2.4=400

64 x 4 + 18 x 4 + 9 x 2 x 4 = 64 x 4 + 18 x 4 + 18 x 4 = (64 + 18 + 18) x 4 = 100 x 4 = 400

400 tk m nhé

\(\frac{3}{9}\cdot\frac{5}{4}=\frac{1}{3}\cdot\frac{5}{4}\)

\(=\frac{1.5}{3.4}\)

\(=\frac{5}{12}\)

3/9=1/3

5/4=5/4(ko rút gọn đc)

3/9x5/4=5/12

NHỚ K CHO MK NHA

15/16

\(\dfrac{6}{9}\)\(\times\dfrac{2}{8}\)=\(\dfrac{2}{3}\times\dfrac{1}{4}\)

         \(=\)\(\dfrac{1}{6}\)

tick mình nhé

= 1/6 

k cho mk nha

HT

=12/72

\(a,\dfrac{5}{4}+\dfrac{7}{3}=\dfrac{15}{12}+\dfrac{28}{12}=\dfrac{43}{12}\\ b,\dfrac{4}{5}\times\dfrac{5}{8}=\dfrac{4}{8}=\dfrac{1}{2}\\ c,\dfrac{2}{3}-\dfrac{3}{8}=\dfrac{16}{24}-\dfrac{9}{24}=\dfrac{7}{24}\\ d,\dfrac{5}{6}:\dfrac{1}{3}=\dfrac{5}{6}\times\dfrac{1}{3}=\dfrac{5}{18}\)

a) \(\dfrac{5}{4}+\dfrac{7}{3}=\dfrac{15}{12}+\dfrac{28}{12}=\dfrac{43}{12}\)

b) \(\dfrac{4}{5}\cdot\dfrac{5}{8}=\dfrac{20}{40}=\dfrac{1}{2}\)

c) \(\dfrac{2}{3}-\dfrac{3}{8}=\dfrac{16}{24}-\dfrac{9}{24}=\dfrac{7}{24}\)

d) \(\dfrac{5}{6}:\dfrac{1}{3}=\dfrac{5}{6}\cdot\dfrac{3}{1}=\dfrac{15}{6}\)

TL

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

\(\frac{7}{5}-\frac{15}{25}=\frac{7}{5}-\frac{3}{5}=\frac{4}{5}\)

\(\frac{3}{2}-\frac{4}{8}=\frac{3}{2}-\frac{1}{2}=\frac{2}{2}\)

nhé

thank you cáo nha

\(=\frac{2^{15}\cdot\left(3^2\right)^4}{2^7\cdot3^7\cdot\left(2^3\right)^3}\) 

\(=\frac{2^{15}\cdot3^8}{2^7\cdot3^7\cdot2^9}\) 

\(=\frac{2^{15}\cdot3^8}{2^{16}\cdot3^7}\) 

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

Bài làm :

\(\frac{2^{15}.9^4}{6^7.8^3}\)

\(=\frac{2^{15}.\left(3^2\right)^4}{\left(2.3\right)^7.(2^3)^3}\)

\(=\frac{2^{15}.3^8}{2^7.3^7.2^9}\)

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

Học tốt nhé

\(\frac{2^{15}.9^4}{6^7.8^3}=\frac{2^{15}.\left(3^2\right)^4}{2^7.3^7.\left(2^3\right)^3}=\frac{2^{15}.3^8}{2^7.3^7.2^9}=\frac{3}{2}\)

học tốt

            Bài làm :

Ta có :

\(\frac{2^{15}.9^4}{6^7.8^3}=\frac{2^{15}.\left(3^2\right)^4}{\left(2.3\right)^7.\left(2^3\right)^3}=\frac{2^{15}.3^8}{2^7.3^72^9}=\frac{3}{2}\)

Bài làm :

\(\frac{2^{15}.9^4}{6^7.8^3}\)

\(=\frac{2^{15}.\left(3^2\right)^4}{\left(2.3\right)^7.\left(2^3\right)^3}\)

\(=\frac{2^{15}.3^8}{2^7.3^7.2^9}\)

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

Học tốt nhé

\(\frac{2^{15}.9^4}{6^7.8^3}\)\(=\frac{2^{15}.\left(3^2\right)^4}{\left(2.3\right)^7.\left(2^3\right)^3}\)\(=\frac{2^{15}.3^8}{2^7.3^7.2^9}\)\(=\frac{2^{15}.3^8}{2^{16}.3^7}\)\(=\frac{1.3^1}{2^1.1}\)\(=\frac{3}{2}\)

CHÚC BẠN HỌC TỐT

Lời giải:

$\frac{1}{2}+\frac{1}{2}=\frac{1+1}{2}=\frac{2}{2}=1$

$\frac{3}{8}+\frac{1}{8}=\frac{3+1}{8}=\frac{4}{8}=\frac{1}{2}$

$\frac{7}{9}+\frac{5}{9}=\frac{7+5}{9}=\frac{12}{9}=\frac{3\times 4}{3\times 3}=\frac{4}{3}$

Sao lại = hả bạn?