HM
0
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
31 tháng 3 2021
B=5/18*21+5/21*24+5/24*27+...+5/123*126
3/5B=3/5(5/18*21+5/21*24+...+5/123*126)
3/5B=3/5*5/18*21+3/5*5/21*24+...+3/5*5/123*126
3/5B=3/18*21+3/21*24+...+3/123*126
3/5B=1/18-1/21+1/21-1/24+...+1/123-1/126
3/5B=1/18-1/126
3/5B=126/2268-18/2268
3/5B=108/2268
3/5B=21
B=21÷3/5
B=21*5/3
B=35
2 tháng 5 2019
\(B=\frac{5}{18\cdot21}+\frac{5}{21\cdot24}+\frac{5}{24\cdot27}+...+\frac{5}{123\cdot126}\\ B=\frac{5}{3}\cdot\left(\frac{3}{18\cdot21}+\frac{3}{21\cdot24}+\frac{3}{24\cdot27}+...+\frac{3}{123\cdot126}\right)\\ B=\frac{5}{3}\cdot\left(\frac{1}{18}-\frac{1}{21}+\frac{1}{21}-\frac{1}{24}+\frac{1}{24}-\frac{1}{27}+...+\frac{1}{123}-\frac{1}{126}\right)\\ B=\frac{5}{3}\cdot\left(\frac{1}{18}-\frac{1}{126}\right)\\ B=\frac{5}{3}\cdot\left(\frac{7}{126}-\frac{1}{126}\right)\\ B=\frac{5}{3}\cdot\frac{1}{21}\\ B=\frac{5}{63}\)
S
1 tháng 2 2024
câu 1)
\(\dfrac{-12}{18}+\left(\dfrac{-21}{35}\right)=\dfrac{-19}{15}\)
câu 2)
\(-\dfrac{3}{21}+\dfrac{6}{42}=0\)
câu 3)
\(-\dfrac{18}{24}+\dfrac{15}{21}=-\dfrac{1}{28}\)
câu 4)
\(\dfrac{1}{6}+\dfrac{2}{5}=\dfrac{17}{30}\)
câu 5)
\(\dfrac{3}{5}+\left(-\dfrac{7}{4}\right)=-\dfrac{23}{20}\)
câu 6)
\(\left(-2\right)+\left(\dfrac{-5}{8}\right)=\dfrac{-21}{8}\)
câu 7)
\(\dfrac{1}{-8}+\left(-\dfrac{5}{9}\right)=-\dfrac{49}{72}\)
câu 8)
\(\dfrac{4}{13}+\dfrac{12}{39}=\dfrac{8}{13}\)
câu 9)
\(\dfrac{1}{21}+\dfrac{1}{28}=\dfrac{1}{12}\)
câu 10)
\(-\dfrac{3}{29}+\dfrac{16}{58}=\dfrac{5}{29}\)
câu 11)
\(\dfrac{8}{40}+\left(-\dfrac{36}{45}\right)=-\dfrac{3}{5}\)
câu 12)
\(-\dfrac{8}{18}+\left(-\dfrac{15}{27}\right)=-1\)
câu 13)
\(\dfrac{13}{30}+\left(-\dfrac{1}{5}\right)=\dfrac{7}{30}\)
câu 14)
\(\dfrac{2}{21}+\dfrac{1}{28}=\dfrac{11}{84}\)
câu 15)
\(5+\left(-\dfrac{3}{4}\right)=\dfrac{17}{4}\)
câu 16)
\(\dfrac{18}{24}+\dfrac{45}{-10}=-\dfrac{15}{4}\)
I
26 tháng 2 2020
A, (-25). 21. (-2)2. (-|-3|). (-1)2015
B, (-5)3. 67. (-|-2|). (-1)2014
C, 35.18 – 5.7.28 + 35. (-90)
D, 24. (16 – 5) – 16. (24 – 5)
E, - 79. (73 – 27) – 73. (-79 + 27)
G, 31. (-18) + 31. (-8)-31
M, -48 + 48. (-78) + 48. (-21)
N, -|-17| + 2. [ 24: (-8) + (-5)2]
I, -|-7|. [(-2)4 + (-36): (-32)] – (-5)3
TV
0
24 tháng 4 2020
Câu 1:
a) Ta có: 2n+1 là số lẻ∀n
⇒\(\left(-1\right)^{2n+1}=-1\)
Ta có: \(\left(-25\right)\cdot21\cdot\left(-2\right)^2\cdot\left(-\left|-3\right|\right)\cdot\left(-1\right)^{2n+1}\)
\(=-25\cdot21\cdot4\cdot\left(-3\right)\cdot\left(-1\right)\)
\(=75\cdot84\cdot\left(-1\right)\)
\(=-6300\)
b) Ta có: \(\left(-5\right)^3\cdot67\cdot\left(-\left|-2^3\right|\right)\cdot\left(-1\right)^{2n}\)
\(=-125\cdot67\cdot\left(-8\right)\)
\(=1000\cdot67=67000\)
c) Ta có: \(35\cdot18-5\cdot7\cdot28\)
\(=35\cdot18-35\cdot28\)
\(=35\cdot\left(18-28\right)=35\cdot\left(-10\right)=-350\)
d) Ta có: \(24\cdot\left(16-5\right)-16\cdot\left(24-5\right)\)
\(=24\cdot16-24\cdot5-24\cdot16+16\cdot5\)
\(=-24\cdot5+16\cdot5\)
\(=5\cdot\left(-24+16\right)=5\cdot\left(-8\right)=-40\)
e) Ta có: \(29\cdot\left(19-13\right)-19\cdot\left(19-13\right)\)
\(=6\cdot\left(29-19\right)=6\cdot10=60\)
g)Sửa đề: \(31\cdot\left(-18\right)+31\cdot\left(-81\right)-31\)
Ta có: \(31\cdot\left(-18\right)+31\cdot\left(-81\right)-31\)
\(=31\cdot\left(-18-81-1\right)\)
\(=31\cdot\left(-100\right)=-3100\)
h) Ta có: \(\left(-12\right)\cdot47+\left(-12\right)\cdot52+\left(-12\right)\)
\(=-12\cdot\left(47+52+1\right)\)
\(=-12\cdot100=-1200\)
k) Ta có: \(13\cdot\left(23+22\right)-3\cdot\left(17+28\right)\)
\(=13\cdot45-3\cdot45\)
\(=45\cdot\left(13-3\right)=45\cdot10=450\)
m) Ta có: \(-48+48\cdot\left(-78\right)+48\cdot\left(-21\right)\)
\(=48\cdot\left(-1-78-21\right)\)
\(=48\cdot\left(-100\right)=-4800\)
n) Ta có: \(135\cdot\left(171-123\right)-171\cdot\left(135-123\right)\)
\(=135\cdot171-135\cdot123-171\cdot135+171\cdot123\)
\(=123\cdot\left(-135+171\right)=123\cdot36=4428\)