Bài tập 87 trang 26 SBT Toán 6 Tập 2

CM: \(\dfrac{5}{3.7}+\dfrac{5}{7.11}+\dfrac{5}{11.15}+.....+\dfrac{3}{\left(4n-1\right)\left(4n+3\right)}=\dfrac{5n}{4n+3}\)

\(\dfrac{3}{7}\)x\(\dfrac{4}{5}\)

\(\dfrac{9}{13}\)x\(\dfrac{5}{4}\) bằng

\(\frac{9}{23}\times\frac{5}{8}+\frac{9}{23}\times\frac{3}{8}-\frac{9}{23}\)=

giup vs

Phát biểu quy tắc nhân hai phân số.

Giúp mình với, mình cần gấp lắm!

tính tích :

3/4*8/9*15/16*...899/900

/: dấu gạch

A=70x(131313/565656+131313/272727+131313/909090)

\(\dfrac{-5}{13}.\dfrac{3}{7}-\dfrac{2}{7}.\dfrac{8}{13}+\dfrac{5}{13}.\dfrac{1}{7}\)

x phần 126 = -5 phần 9 nhân 4 phần 7

THỰC HIỆN PHÉP TÍNH SAU:

a/\(\dfrac{1}{1.2}\)+\(\dfrac{1}{2.3}\)+\(\dfrac{1}{3.4}\)+...........+\(\dfrac{1}{99.100}\)

b/\(\dfrac{5.4^{15}-9^9-4.3^{10}.8^9}{5.29-6^{19}.7.2^{29}.27^6}\)

Chứng tỏ

\(1-\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{99}-\dfrac{1}{100}=\dfrac{1}{51}+\dfrac{1}{52}+...+\dfrac{1}{100}\)

tìm x:

\(\left(1-\dfrac{1}{2}\right)\cdot\left(1-\dfrac{1}{3}\right)\cdot\left(1-\dfrac{1}{4}\right)\cdot...\cdot\left(1-\dfrac{1}{10}\right)=\dfrac{x}{2010}\)

Tìm x;

a,\(\left(1-\dfrac{1}{3}\right)\)*\(\left(1-\dfrac{1}{6}\right)\)*\(\left(1-\dfrac{1}{10}\right)\)*...*\(\left(1-\dfrac{1}{780}\right)\)*x=1

C=\(\dfrac{2}{15}+\dfrac{2}{35}+\dfrac{2}{63}+...+\dfrac{2}{399}\)

E=\(\dfrac{6}{1.3.7}+\dfrac{6}{6.7.9}+...+\dfrac{6}{13.15.19}\)

F=\(\dfrac{92-\dfrac{1}{9}-\dfrac{2}{10}-\dfrac{3}{11}-...-\dfrac{92}{100}}{\dfrac{1}{9}+\dfrac{1}{10}+...+\dfrac{1}{100}}\)

G=\(10-\dfrac{1}{72}-\dfrac{1}{56}-\dfrac{1}{42}-...-\dfrac{1}{6}-\dfrac{1}{2}\)

Tính một cách hợp lý:

a\(\left(\dfrac{1}{2}-1\right)\left(\dfrac{1}{3}-1\right)...\left(\dfrac{1}{100}-1\right)\)) \(x:\dfrac{99}{100}:\dfrac{98}{99}:...:\dfrac{2}{3}:\dfrac{1}{2}\)

b) \(\dfrac{5-\dfrac{5}{3}+\dfrac{5}{9}-\dfrac{5}{27}}{8-\dfrac{8}{3}+\dfrac{8}{9}-\dfrac{8}{27}}:\dfrac{15-\dfrac{15}{11}+\dfrac{15}{121}}{16-\dfrac{16}{11}+\dfrac{16}{121}}\)

c) \(\dfrac{\dfrac{1}{9}-\dfrac{5}{6}-4}{\dfrac{7}{12}-\dfrac{1}{36}-10}\)

d) \(\left(\dfrac{1}{2}+1\right)\left(\dfrac{1}{3}+1\right)...\left(\dfrac{1}{99}+1\right)\)

e)

-15/12 . x+ 3/7=6/5 .x -1/2

. Giúp mình chuẩn bị thi

(1+\(\dfrac{1}{100}\)). (1+\(\dfrac{1}{101}\)).(1+\(\dfrac{1}{102}\))....(1+\(\dfrac{1}{2018}\))

CMR:1×3×5×7×...×19=11/2×12/2×13/2×...×20/2

các bạn giúp mình nhé mình đang cần gấp ạ

a.\(\dfrac{5}{-4}\).\(\dfrac{16}{25}\)+\(\dfrac{-5}{4}\).\(\dfrac{9}{25}\) (. là nhân nhé ạ ) e.\(11\dfrac{1}{4}\)-(\(2\dfrac{5}{7}\)_⁺\(5\dfrac{1}{4}\))

b.\(4\dfrac{11}{23}\)-\(\dfrac{9}{14}\)+\(2\dfrac{12}{23}\)-\(\dfrac{5}{4}\) g.\(\dfrac{7}{19}\).\(\dfrac{8}{11}\)+\(\dfrac{7}{19}\).\(\dfrac{3}{11}\)+\(\dfrac{12}{19}\)

c.\(2\dfrac{13}{27}\)-\(\dfrac{7}{15}\)+\(3\dfrac{14}{27}\)-\(\dfrac{8}{15}\) h.\(-\left(\dfrac{1}{2}\right)^2\) .13\(\dfrac{9}{11}\)-25%.6\(\dfrac{2}{11}\)

d.\(\dfrac{-4}{9}\).\(\dfrac{7}{15}\)+\(\dfrac{4}{-9}\).\(\dfrac{8}{15}\) i.57%+1\(\dfrac{2}{15}\):\(\dfrac{68}{25}\)-2,82

\(\dfrac{1}{2}\).(\(\dfrac{2}{9}\)+\(\dfrac{3}{7}\)-\(\dfrac{5}{27}\))

Chứng tỏ rằng : \(\dfrac{31}{2}\) . \(\dfrac{32}{2}\) . \(\dfrac{33}{2}\) . .... . \(\dfrac{60}{2}\) = 1 . 3 . 5.... 59

Tính

S = 1/1.2+1/2.3+1/3.4+1/4.5

P= 1/1.3+1/3.5+1/5.7+1/7.9

Tính;

a) \(\dfrac{-7}{9}\) . 2\(\dfrac{3}{4}\) b) \(\dfrac{2}{3}\) + \(\dfrac{1}{3}\) . \(\dfrac{-2}{5}\)

c) \(\dfrac{2}{3}\) - 4 (\(\dfrac{1}{2}\)+\(\dfrac{3}{4}\)) d) (\(\dfrac{1}{-3}\) + \(\dfrac{5}{6}\)) .11-7

e)\(\dfrac{3}{4}\) . 15\(\dfrac{1}{3}\) - \(\dfrac{3}{4}\) . 43\(\dfrac{1}{3}\)