a) 10/9

b) 15/8

c) 35/2

d) 72/175

b)  2 - 8/9 = 10/9    

c) 5/8 x 3 = 15/8

d) 5 : 6/21= 105/6             

đ) 3/5 x 4/5 x 6/7= 72/175

a) 10/9

b) 15/8

c) 35/2

d) 72/175

\(B=\frac{\left(1,09-0,29\right).1\frac{1}{4}}{\left(18,9-16\frac{13}{20}\right).\frac{8}{9}}=\frac{0,8.\frac{5}{4}}{\left[\left(18+0,9\right)-\left(16+\frac{13}{20}\right)\right].\frac{8}{9}}\)

\(B=\frac{\frac{4}{5}.\frac{5}{4}}{\left(18+\frac{9}{10}-16-\frac{13}{20}\right).\frac{8}{9}}\)

\(B=\frac{1}{\left[\left(18-16\right)+\left(\frac{9}{10}-\frac{13}{20}\right)\right].\frac{8}{9}}\)

\(B=\frac{1}{\left(2+\frac{1}{4}\right).\frac{8}{9}}\)

\(B=\frac{1}{\frac{9}{4}.\frac{8}{9}}=\frac{1}{2}\)

7 / 4 - 5/8 = 14 / 8 - 5 / 8 = 9/8

9 / 1 . 3 / 11 = 27 / 11

1/2 . 5 / 2 = 5 / 4

\(\dfrac{7}{4}-\dfrac{5}{8}=\dfrac{14}{8}-\dfrac{5}{8}=\dfrac{9}{8}\)

\(9\times\dfrac{3}{11}=\dfrac{9\times3}{11}=\dfrac{27}{11}\)

\(\dfrac{1}{2}:\dfrac{2}{5}=\dfrac{1}{2}\times\dfrac{5}{2}=\dfrac{5}{4}\)

Bài 7: Tính

b) 7/4 - 5/8=7/4-5/8=14/8-5/8=9/8

c) 9 x 3/11=9/1.3/11=27/11

d) 1/2 : 2/5=1/2.5/2=5/4

\(B=1+5+5^2+5^3+....+5^{2009}\)

=> \(5B=5+5^2+5^3+5^4+....+5^{2010}\)

=> \(4B=5^{2010}-1\)

=> \(B=\frac{5^{2010}-1}{4}\)

Study well ! >_<

các bạn giúp mình với ai trả lời nhanh nhất mình sẽ h cho bạn ấy

\(B=\left(17+\dfrac{1}{25}-16-\dfrac{11}{15}\right)\cdot\dfrac{75}{23}+\dfrac{75}{23}\cdot\dfrac{23}{75}\)

\(=\dfrac{23}{75}\cdot\dfrac{75}{23}+1=1+1=2\)

-180

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