Tinh gia tri cua bieu thuc \(D=\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{200}\)
Nho giai va tring bay cach lam cho minh luon nha ^_^
bai 1 :thuc hien phep tinh
a)\(\frac{-5}{2}:\left(\frac{3}{4}-\frac{1}{2}\right)\) b) \(11\frac{3}{13}-\left(2\frac{4}{7}+5\frac{3}{13}\right)\) c)\(\left(\frac{-5}{24}+0,75+\frac{7}{12}\right):\left(-2\frac{1}{4}\right)^2\)
AI LAM NHANH VA DUNG THI MK SE TICK CHO NHA
MK DAG CAN GAP !!!!!!! CAC BAN LAM NHANH LEN NHA
Tinh gia tri cua bieu thuc \(D=\frac{1}{6}+\frac{1}{10}+\frac{1}{15}+\frac{1}{21}+\frac{1}{28}+\frac{1}{36}+\frac{1}{45}\)
Nho giai va trinh bay cach lam cho minh luon nha ^_^
1/2D=1/2(1/6+1/10+......+1/45)
1/2D=1/12+1/20+1/30+.....+1/90
1/2D=1/3.4+1/4.5+1/5.6+......+1/9.10
1/2D=1/3-1/4+1/4-1/5+1/5-1/6+....+1/9-1/10
1/2D=1/3-1/10
1/2D=7/30
D=7/30:1/2
D=7/15
Ta có:\(D=\frac{1}{6}+\frac{1}{10}+\frac{1}{15}+\frac{1}{21}+\frac{1}{28}+\frac{1}{36}+\frac{1}{45}\)
\(=\frac{2}{12}+\frac{2}{20}+\frac{2}{30}+\frac{2}{42}+\frac{2}{56}+\frac{2}{72}+\frac{2}{90}\)
\(=2.\left(\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}\right)\)
\(=2.\left(\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}\right)\)
\(=2.\left(\frac{1}{3}-\frac{1}{10}\right)=2.\frac{7}{30}=\frac{7}{15}\)
Vậy \(D=\frac{7}{15}\)
không biết làm
bai 1 : thuc hien phep tinh:
a) \(\frac{-5}{2}\)\(:\left(\frac{3}{4}-\frac{1}{2}\right)\) b) \(11\frac{3}{13}-\left(2\frac{4}{7}+5\frac{3}{13}\right)\) c) \(\left(\frac{-5}{24}+0,75+\frac{7}{12}\right):\left(-2\frac{1}{4}\right)^2\)
AI LAM NHANH VA DUNG THI MK SE TICK CHO NGUOI DO HIHI ^_^
a)\(=\frac{-5}{2}:\left(\frac{3}{4}-\frac{2}{4}\right)\)
\(=\frac{-5}{2}:1=\frac{-5}{2}\)
b)\(=\frac{146}{13}-\left(\frac{18}{7}+\frac{68}{13}\right)\)
\(=\frac{146}{13}-\frac{18}{7}-\frac{68}{13}\)
\(=\frac{146}{13}-\frac{68}{13}-\frac{18}{7}\)
\(=\frac{78}{13}-\frac{18}{7}=6-\frac{18}{7}=\frac{42}{7}-\frac{18}{7}=\frac{24}{7}\)
c)\(=\left(\frac{-5}{24}+\frac{18}{24}+\frac{14}{24}\right):\left(\frac{-9}{4}\right)^2\)
\(=\frac{27}{24}:\frac{\left(-9\right)^2}{4^2}\)
\(=\frac{27\times16}{24\times81}=\frac{2}{9}\)
tinh gia try bieu thuc
A=\(\left[\frac{1}{7}+\frac{1}{23}-\frac{1}{1009}\right]:\left[\frac{1}{23}+\frac{1}{7}-\frac{1}{1009}+\frac{1}{7}\times\frac{1}{23}\times\frac{1}{1009}\right]+1:\left[30\times1009-160\right]\)
ai lam dung co ca cach lam cho 1 like
bài 1 cho a,b,c là 3 độ dài 3 cạnh tam giác
CMR \(\frac{1}{a+b-c}+\frac{1}{b+c-a}+\frac{1}{a+c-b}>=\frac{1}{a}+\frac{1}{b}+\frac{1}{c}\)
co ai biet lam k lam giup minh di. minh dang can lam. cac ban than dong tren OLM giup minh di
\(Cho\:A=\frac{1}{11}+\frac{1}{12}+\frac{1}{13}+...+\frac{1}{70}\)
a) Chứng minh A lớn hơn hoặc bằng \(\frac{4}{3}\)
b) Chứng minh A bé hơn hoặc bằng 2,5
Cho A=\(\frac{1}{11}+\frac{1}{12}+...+\frac{1}{70}CMR:\frac{4}{3}< A< \frac{5}{2}\)
Bạn vô câu hỏi tương tự để tham khảo nha!!!
Cho A=\(\frac{1}{11}+\frac{1}{12}+\frac{1}{13}+...+\frac{1}{70}.Chungminhrang\frac{4}{3}< A< \frac{5}{2}\)
