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\(\frac{1}{2}:0,5-\frac{1}{4}:0,25+\frac{1}{8};0,125-\frac{1}{10}:0,1=\frac{1}{2}:\frac{1}{2}-\frac{1}{4}:\frac{1}{4}+\frac{1}{8}:\frac{1}{8}-\frac{1}{10}:\frac{1}{10}=1-1+1-1=0+0=0\)
em ơi cái này = 0 . Anh chắc chắn vs em 100000000000000000000000000000000000000000000000000000000000000000%
Anh lớp 7 mà
Chỗ cuối mk nhầm, sửa lại nha :
\(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+...+\frac{1}{90}+\frac{1}{100}\)
\(=\frac{1}{2\times3}+\frac{1}{3\times4}+\frac{1}{4\times5}+\frac{1}{5\times6}+...+\frac{1}{9\times10}+\frac{1}{100}\)
\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+...+\frac{1}{9}-\frac{1}{10}+\frac{1}{100}\)
\(=\frac{1}{2}-\frac{1}{10}+\frac{1}{100}\)
\(=\frac{50}{100}-\frac{10}{100}+\frac{1}{100}\)
\(=\frac{41}{100}\)
\(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+...+\frac{1}{90}+\frac{1}{100}\)
\(=\frac{1}{2\times3}+\frac{1}{3\times4}+\frac{1}{4\times5}+\frac{1}{5\times6}+...+\frac{1}{9\times10}+\frac{1}{100}\)
\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+...+\frac{1}{9}-\frac{1}{10}+\frac{1}{100}\)
\(=\frac{1}{2}-\frac{1}{10}+\frac{1}{100}\)
\(=\frac{50}{100}-\frac{10}{100}-\frac{1}{100}\)
\(=\frac{39}{100}\)
Đúng thì k nha bn !!!!
1/6 + 1/12 + 1/20 + 1/30 + 1/42 + ... + 1/90 + 1/110 = 1/2.3 + 1/3.4 + 1/4.5 + 1/5.6 + 1/6.7 + ... + 1/9.10 + 1/10.11 = 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6 + 1/6 - 1/7 + ... + 1/9 - 1/10 + 1/10 - 1/11 = 1/2 - 1/11 = 9/22
\(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{90}+\frac{1}{110}\)
=\(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{9.10}+\frac{1}{10.11}\)
=\(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{9}-\frac{1}{10}+\frac{1}{10}-\frac{1}{11}\)
=\(\frac{1}{2}-\frac{1}{11}\)
=\(\frac{9}{22}\)
\(\left(y-\frac{1}{2}\right):\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{90}\right)=\frac{1}{3}\)
=> \(\left(y-\frac{1}{2}\right):\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{9.10}\right)=\frac{1}{3}\)
=> \(\left(y-\frac{1}{2}\right):\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{9}-\frac{1}{10}\right)=\frac{1}{3}\)
=> \(\left(y-\frac{1}{2}\right):\left(1-\frac{1}{10}\right)=\frac{1}{3}\)
=> \(\left(y-\frac{1}{2}\right):\frac{9}{10}=\frac{1}{3}\)
=> \(y-\frac{1}{2}=\frac{3}{10}\)
=> \(y=\frac{13}{10}\)
Study well ! >_<
\(\frac{1}{31}+\frac{1}{32}+...........+\frac{1}{89}+\frac{1}{90}>\frac{5}{6}\)
A = 1 / 31 + 1 / 32 + 1 / 33 + ... + 1 / 89 + 1 / 90 ... 5 / 6
A = 5 / 6 = 1 / 2 + 1 / 3
Ta đặt B = 1 / 31 + 1 / 32 + 1 / 33 + ... + 1 / 60 ( 30 phân số )
C = 1 / 61 + 1 / 62 + 1 / 63 + ... + 1 / 90 ( 30 phân số )
Ta có : B = 1 / 31 + 1 / 32 + 1 / 33 + ... + 1 / 60 > 1 / 60 + 1 / 60 + 1 / 60 + ... + 1 / 60 = 30 . 1 / 60 = 1 / 2
C = 1 / 61 + 1 / 62 + 1 / 63 + ... + 1 / 90 > 1 / 90 + 1 / 90 + 1 / 90 + ... + 1 / 90 = 30 . 1 / 90 = 1 / 3
Vì A = B + C > 1 / 2 + 1 / 3 = 5 / 6 nên 1 / 31 + 1 / 32 + ... + 1 / 89 + 1 / 90 > 5 / 6
GIẢI VẦY MỚI GỌI LÀ GIẢI CHI TIẾT
Ta sẽ lấy
\(1-\frac{1}{90}=\frac{89}{90}\)
Sau đó ta so sánh :
\(\frac{89}{90}>\frac{5}{6}\)
k mình nhé !!!