K
Khách
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Các câu hỏi dưới đây có thể giống với câu hỏi trên
17 tháng 2 2020
\(B=\frac{1}{1\cdot2\cdot3}+\frac{1}{2\cdot3\cdot4}+\frac{1}{3\cdot4\cdot5}+\frac{1}{18\cdot19\cdot20}\)
\(B=\frac{1}{2}\left(\frac{2}{1\cdot2\cdot3}+\frac{2}{2\cdot3\cdot4}+\frac{2}{3\cdot4\cdot5}+\frac{2}{18\cdot19\cdot20}\right)\)
\(B=\frac{1}{2}\left(\frac{1}{1\cdot2}-\frac{1}{2\cdot3}+\frac{1}{2\cdot3}-\frac{1}{3\cdot4}+\frac{1}{3\cdot4}-\frac{1}{4\cdot5}+...+\frac{1}{18\cdot19}-\frac{1}{19\cdot20}\right)\)
\(B=\frac{1}{2}\left(\frac{1}{1\cdot2}-\frac{1}{19\cdot20}\right)\)
\(B=\frac{1}{2}\cdot\frac{189}{380}=\frac{189}{760}\)
\(C=\frac{52}{1\cdot6}+\frac{52}{6\cdot11}+\frac{52}{11\cdot16}+...+\frac{52}{31\cdot36}\)
\(C=\frac{52}{5}\left(\frac{5}{1\cdot6}+\frac{5}{6\cdot11}+\frac{5}{11\cdot16}+...+\frac{6}{31\cdot36}\right)\)
\(C=\frac{52}{5}\left(1-\frac{1}{6}+\frac{1}{6}-\frac{1}{11}+\frac{1}{11}-\frac{1}{16}+...+\frac{1}{31}-\frac{1}{36}\right)\)
\(C=\frac{52}{5}\cdot\left(1-\frac{1}{36}\right)\)
\(C=\frac{91}{9}\)
LQ
7
28 tháng 9 2018
34 + 52 : ( x + 1 ) = 13 . 3
34 + 25 : ( x + 1 ) = 39
25 : ( x + 1 ) = 39 - 34
25 : ( x + 1 ) = 5
x + 1 = 25 : 5
x + 1 = 5
x = 6
SN
28 tháng 9 2018
+ >34 + 52 : ( x + 1) = 13.3
52 : ( x + 1)= 39-34
52 : ( x + 1)=5
x + 1 = 5
x = 5-1
x = 4
+> 11+ 23 . 3 ( x - 13 ) = 35
23 . 3 ( x - 13 ) = 35 - 11
23 . 3 ( x - 13 )= 24
3 ( x - 13 )= 3
x - 13= 3:3
x - 13=1
x= 1+13
x= 14
AN
26 tháng 4 2019
Bài 1:
\(\frac{3}{7}\cdot\frac{9}{2}-\frac{1}{14}\cdot\frac{1}{13}\)=\(\frac{27}{14}-\frac{1}{14}\cdot\frac{1}{13}\)
= \(\frac{1}{14}\left(27-\frac{1}{3}\right)\)
= \(\frac{1}{14}\cdot\frac{350}{13}\)=\(\frac{25}{13}\)
bài 2:\(\frac{5}{9}\cdot\frac{7}{13}+\frac{5}{9}\cdot\frac{9}{13}\cdot\frac{3}{13}\)= \(\frac{5}{9}\cdot\frac{1}{13}\left(7+9\cdot\frac{3}{13}\right)\)
= \(\frac{5}{9}\cdot\frac{1}{13}\cdot\frac{94}{13}\)=\(\frac{470}{1521}\)
có j sai xin mn chỉ bảo!
NH
7 tháng 8 2021
Câu 13 :
\(\left(-\frac{1}{4}+\frac{5}{8}\right)+-\frac{3}{5}\)
\(=\frac{3}{8}-\frac{-3}{5}\)
\(=\frac{39}{40}\)
Câu 14 :
\(M=\frac{5}{9}.\frac{7}{13}+\frac{5}{9}.\frac{9}{13}-\frac{5}{9}.\frac{3}{13}\)
\(=\frac{5}{9}.\left(\frac{7}{13}+\frac{9}{13}-\frac{3}{13}\right)\)
\(=\frac{5}{9}.1=\frac{5}{9}\)
Câu 15 :
\(E=\left(-\frac{3}{4}+\frac{2}{5}\right):\frac{3}{7}+\left(\frac{3}{5}+\frac{-1}{4}\right):\frac{3}{7}\)
\(E=\left(-\frac{3}{4}+\frac{2}{5}+\frac{3}{5}+\frac{-1}{4}\right):\frac{3}{7}\)
\(E=0\)
Câu 16 :
\(H=\frac{7}{8}:\left(\frac{2}{9}-\frac{1}{8}\right)+\frac{7}{8}:\left(\frac{1}{36}-\frac{5}{12}\right)\)
\(=\frac{7}{8}:\left(\frac{2}{9}-\frac{1}{8}+\frac{1}{36}-\frac{5}{12}\right)\)
\(=\frac{7}{8}:\frac{-7}{24}=-3\)
7 tháng 8 2021
huhuhuhuhuhuhuhuhuhuhuhuhu giúp mk đi
Plssssssssssssssssssssssssssssssssssssssssssssss
16 tháng 4 2023
a) 5/17 * 8/-7+8/17*-7/3+-7/3*4/17
-40/119 + 12/17 × -7/3
-40/119 + -28/17 =-236/119
b) -10/13 + 5/17 - 3/13 + 12/17 - 11/20
(5/17+12/17)-(10/13+3/13)-11/20
-11/20
17 tháng 4 2023
a) 5/17 * 8/-7+8/17*-7/3+-7/3*4/17
-40/119 + 12/17 × -7/3
-40/119 + -28/17 =-236/119
b) -10/13 + 5/17 - 3/13 + 12/17 - 11/20
(5/17+12/17)-(10/13+3/13)-11/20
-11/20
2 tháng 8 2016
\(\frac{1}{1.2}+\frac{5}{2.7}+\frac{9}{7.16}+\frac{13}{16.29}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{7}+\frac{1}{7}-\frac{1}{16}+\frac{1}{16}-\frac{1}{29}\)
\(=1-\frac{1}{29}=\frac{28}{29}\)
18 tháng 4 2023
\(1,-\dfrac{4}{7}+\dfrac{2}{3}\times\dfrac{-9}{14}\)
\(=\dfrac{-4}{7}+\dfrac{-18}{42}\)
\(=\dfrac{-4\times6}{7\times6}+\dfrac{-18}{42}\)
\(=\dfrac{-20}{42}+\dfrac{-18}{42}\)
\(=-\dfrac{38}{42}\)
\(=-\dfrac{19}{21}\)
\(2,\dfrac{17}{13}-\left(\dfrac{4}{13}-11\right)\)
\(=\dfrac{17}{13}-\dfrac{4}{13}+11\)
\(=\dfrac{13}{13}+11\)
\(=1+11\)
\(=12\)
\(3,8\dfrac{2}{7}-\left(3\dfrac{4}{9}+4\dfrac{2}{7}\right)\)
\(=\dfrac{58}{7}-\left(\dfrac{31}{9}+\dfrac{30}{7}\right)\)
\(=\dfrac{58}{7}-\dfrac{31}{9}-\dfrac{30}{7}\)
\(=\dfrac{58}{7}-\dfrac{30}{7}-\dfrac{31}{9}\)
\(=\dfrac{28}{7}-\dfrac{31}{9}\)
\(=\dfrac{28\times9}{7\times9}-\dfrac{31\times7}{9\times7}\)
\(=\dfrac{252}{63}-\dfrac{217}{63}\)
\(=\dfrac{35}{63}\)
\(=\dfrac{5}{9}\)
\(5,\left(\dfrac{2}{3}-1\dfrac{1}{2}\right):\dfrac{4}{3}+\dfrac{1}{2}\)
\(=\left(\dfrac{2}{3}-\dfrac{3}{2}\right):\dfrac{4}{3}+\dfrac{1}{2}\)
\(=\left(\dfrac{2\times2}{3\times2}-\dfrac{3\times3}{2\times3}\right):\dfrac{4}{3}+\dfrac{1}{2}\)
\(=\left(\dfrac{4}{6}-\dfrac{9}{6}\right):\dfrac{4}{3}+\dfrac{1}{2}\)
\(=\dfrac{-5}{6}:\dfrac{4}{3}+\dfrac{1}{2}\)
\(=\dfrac{-5}{6}\times\dfrac{3}{4}+\dfrac{1}{2}\)
\(=\dfrac{-15}{24}+\dfrac{1}{2}\)
\(=\dfrac{-15}{24}+\dfrac{1\times12}{2\times12}\)
\(=\dfrac{-15}{24}+\dfrac{12}{24}\)
\(=\dfrac{-3}{24}\)
\(=-\dfrac{1}{8}\)
\(6,\dfrac{-5}{13}+\dfrac{2}{5}+\dfrac{-8}{13}+\dfrac{3}{5}-\dfrac{3}{7}\)
\(=\left(\dfrac{-5}{13}+\dfrac{-8}{13}\right)+\left(\dfrac{2}{5}+\dfrac{3}{5}\right)-\dfrac{3}{7}\)
\(=\dfrac{-13}{13}+\dfrac{5}{5}-\dfrac{3}{7}\)
\(=-1+1-\dfrac{3}{7}\)
\(=-\dfrac{3}{7}\)
\(7,\dfrac{6}{5}\times\dfrac{3}{7}+\dfrac{6}{5}:\dfrac{7}{10}+\dfrac{6}{5}\)
\(=\dfrac{6}{5}\times\dfrac{3}{7}+\dfrac{6}{5}\times\dfrac{10}{7}+\dfrac{6}{5}\)
\(=\dfrac{6}{5}\times\left(\dfrac{3}{7}+\dfrac{10}{7}+1\right)\)
\(=\dfrac{6}{5}\times\left(\dfrac{3}{7}+\dfrac{10}{7}+\dfrac{1\times7}{1\times7}\right)\)
\(=\dfrac{6}{5}\times\left(\dfrac{3}{7}+\dfrac{10}{7}+\dfrac{7}{7}\right)\)
\(=\dfrac{6}{5}\times\dfrac{20}{7}\)
\(=\dfrac{120}{35}\)
\(=\dfrac{24}{7}\)
HQ
Hà Quang Minh
Giáo viên
5 tháng 10 2023
a) \(\dfrac{6}{{13}}.\dfrac{8}{{7}}.\dfrac{{ - 26}}{3}.\dfrac{{ - 7}}{8}\)
\(\begin{array}{l} = \left( {\dfrac{6}{{13}}.\dfrac{{ - 26}}{3}} \right).\left( {\dfrac{8}{7}.\dfrac{{ - 7}}{8}} \right)\\ = \dfrac{{6.\left( { - 26} \right)}}{{13.3}}.\dfrac{{8.\left( { - 7} \right)}}{{7.8}}\\= (- 4).\left( { - 1} \right) = 4\end{array}\)
b) \(\dfrac{6}{5}.\dfrac{3}{{13}} - \dfrac{6}{5}.\dfrac{{16}}{{13}}\)
\(\begin{array}{l} = \dfrac{6}{5}.\left( {\dfrac{3}{{13}} - \dfrac{{16}}{{13}}} \right)\\ = \dfrac{6}{5}.\dfrac{{3 - 16}}{{13}}\\ = \dfrac{6}{5}.\dfrac{{-13}}{{13}}\\= \dfrac{6}{5}.\left( { - 1} \right)\\ = \dfrac{{ - 6}}{5}\end{array}\)
3/7. 5/13 - 8/13 . 3/7 + 3/7.16/13
= 3/7 . ( 5/13 - 8/13 + 16/13 )
= 3/7 . ( 5/13 + -8/13 + 16/13)
= 3/7 .13/13
=3/7 . 1
= 3/7