898019 : 49 =???????????
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Khách
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O
11 tháng 5 2022
\(B=\dfrac{49}{2\cdot9}+\dfrac{49}{9\cdot16}+\dfrac{49}{16\cdot23}+...+\dfrac{49}{65\cdot72}\)
\(B=\dfrac{49}{7}\cdot\left(\dfrac{1}{2}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{16}+\dfrac{1}{16}-\dfrac{1}{23}+...+\dfrac{1}{65}-\dfrac{1}{72}\right)\)
\(B=7\cdot\left(\dfrac{1}{2}-\dfrac{1}{72}\right)\)
\(B=7\cdot\left(\dfrac{36}{72}-\dfrac{1}{72}\right)\)
\(B=7\cdot\dfrac{35}{72}\)
\(B=\dfrac{\left(7\cdot35\right)}{72}\)
\(B=\dfrac{245}{72}\)
11 tháng 5 2022
\(\dfrac{B}{7}=\dfrac{7}{2\cdot9}+\dfrac{7}{9\cdot16}+\dfrac{7}{16\cdot23}+...+\dfrac{49}{65\cdot72}\\ \dfrac{B}{7}=\dfrac{1}{2}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{16}+\dfrac{1}{16}-\dfrac{1}{23}+...+\dfrac{1}{65}-\dfrac{1}{72}\\ \dfrac{B}{7}=\dfrac{1}{2}-\dfrac{1}{72}\\ \dfrac{B}{7}=\dfrac{35}{72}\\ B=\dfrac{35}{72}\times7\\ B=\dfrac{245}{72} \)
RM
1
1 tháng 8 2015
(1/49-1/9)(1/49-1/16).....(1/49-1/49)...(1/49-1/2401)
(1/49-1/9)(1/49-1/16).....0....(1/49-1/2401)
=0
vì khoảng cách là 7 mà 49 chia hết cho 7 nên có phân số 1/49 trong dãy
16 tháng 11 2021
1/ What is your name ?
2/ My name is Andy.
3/ What is this?
4/ It’s a book.
5/ What color is this?
6/ It’s a blue pencil.
PM
2
KN
2 tháng 8 2020
ĐKXĐ : x khác 49 , x khác 50
Ta có :
\(\frac{x-49}{50}+\frac{x-50}{49}=\frac{49}{x-50}+\frac{50}{x-49}\)
\(\Leftrightarrow\frac{x-49}{50}-1+\frac{x-50}{49}-1=\frac{49}{x-50}-1+\frac{50}{x-49}-1\)
\(\Leftrightarrow\frac{x-99}{50}+\frac{x-99}{49}=\frac{99-x}{x-50}+\frac{99-x}{x-49}\)
\(\Leftrightarrow\left(x-99\right)\left(\frac{1}{50}+\frac{1}{49}+\frac{1}{x-50}+\frac{1}{x-49}\right)=0\)
Mà 1/50 + 1/49 + 1/x-50 + 1/x-49 khác 0
\(\Leftrightarrow x-99=0\)
\(\Leftrightarrow x=99\)
2 tháng 8 2020
@Kyo-kun
\(\Leftrightarrow\left(x-99\right)\left(\frac{1}{50}+\frac{1}{x-50}+\frac{1}{49}+\frac{1}{x-49}\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x-99=0\\\frac{x}{50\left(x-50\right)}+\frac{x}{49\left(x-49\right)}=0\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=99\\x\left(\frac{1}{50\left(x-50\right)}+\frac{1}{49\left(x-49\right)}\right)=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=99\\x=0\end{cases}\left(t.m\right)}}\)
Vậy x = 99 hoặc x = 0
PH
1
3 tháng 9 2017
\(F=\dfrac{49}{2.9}+\dfrac{49}{9.16}+............+\dfrac{49}{65.72}\)
\(\Leftrightarrow F=\dfrac{7^2}{2.9}+\dfrac{7^2}{9.16}+............+\dfrac{7^2}{65.72}\)
\(\Leftrightarrow F=7\left(\dfrac{7}{2.9}+\dfrac{7}{9.16}+.............+\dfrac{7}{65.72}\right)\)
\(\Leftrightarrow F=7\left(\dfrac{1}{2}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{16}+...........+\dfrac{1}{65}-\dfrac{1}{75}\right)\)
\(\Leftrightarrow F=7\left(\dfrac{1}{2}-\dfrac{1}{72}\right)\)
\(\Leftrightarrow F=7.\dfrac{35}{72}=\dfrac{245}{72}\)
\(G=\dfrac{3}{1.3}+\dfrac{3}{3.5}+...........+\dfrac{3}{47.49}\)
\(\Leftrightarrow G=\dfrac{3.2}{1.3.2}+\dfrac{3.2}{3.5.2}+........+\dfrac{3.2}{47.49}\)
\(\Leftrightarrow G=\dfrac{3}{2}\left(\dfrac{2}{1.3}+\dfrac{2}{3.5}+..........+\dfrac{2}{47.49}\right)\)
\(\Leftrightarrow G=\dfrac{3}{2}\left(1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+........+\dfrac{1}{47}-\dfrac{1}{49}\right)\)
\(\Leftrightarrow G=\dfrac{3}{2}\left(1-\dfrac{1}{49}\right)\)
\(\Leftrightarrow G=\dfrac{3}{2}.\dfrac{48}{49}=\dfrac{72}{49}\)
29 tháng 12 2016
-49 - 49 x 49 = -49 - 2401
=-2450
29 tháng 12 2016
\(\left(-49\right)-49\cdot49=\left(-49\right)-\left[49\cdot49\right]=\left(-49\right)-2401=-2450\)
k mình
k lại
TM
1
VN
Võ Ngọc Phương
CTVHS
VIP
18 tháng 7 2023
\(\dfrac{11}{49}\times\dfrac{1}{2}+\dfrac{11}{49}:\dfrac{5}{4}-\dfrac{11}{49}\times\dfrac{3}{4}\)
\(=\dfrac{11}{49}\times\dfrac{1}{2}+\dfrac{11}{49}\times\dfrac{4}{5}-\dfrac{11}{49}\times\dfrac{3}{4}\)
\(=\dfrac{11}{49}\times\left(\dfrac{1}{2}+\dfrac{4}{5}-\dfrac{3}{4}\right)\)
\(=\dfrac{11}{49}\times\left(\dfrac{10}{20}+\dfrac{16}{20}-\dfrac{15}{20}\right)\)
\(=\dfrac{11}{49}\times\dfrac{11}{20}\)
\(=\dfrac{121}{980}\)
Chúc bạn học tốt
18 tháng 7 2023
`@` `\text {Ans}`
`\downarrow`
\(\dfrac{11}{49}\times\dfrac{1}{2}+\dfrac{11}{49}\div\dfrac{5}{4}-\dfrac{11}{49}\times\dfrac{3}{4}\)
`=`\(\dfrac{11}{49}\times\dfrac{1}{2}+\dfrac{11}{49}\times\dfrac{4}{5}-\dfrac{11}{49}\times\dfrac{3}{4}\)
`=`\(\dfrac{11}{49}\times\left(\dfrac{1}{2}+\dfrac{4}{5}-\dfrac{3}{4}\right)\)
`=`\(\dfrac{11}{49}\times\dfrac{11}{20}\)
`=`\(\dfrac{121}{980}\)