Tính
1 + ______1________
1+ ______1_______
1+ _____1_______
1+ \(\frac{1}{3}\)
Ps: Đề bài không hề nhầm lẫn
K
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Những câu hỏi liên quan
PT
24 tháng 4 2016
\(A=\frac{1}{5\cdot6}+\frac{1}{6\cdot7}+\frac{1}{7\cdot8}+......+\frac{1}{14\cdot15}\)
\(A=\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+.......+\frac{1}{14}-\frac{1}{15}\)
\(A=\frac{1}{5}-\frac{1}{15}\)
\(A=\frac{3}{15}-\frac{1}{15}\)
\(A=\frac{2}{15}\)
LT
4 tháng 11 2017
Bài 1:
a) \(2\frac{1}{4}+1\frac{1}{2}-1\frac{4}{5}\)
=\(\frac{9}{4}\)+\(\frac{3}{2}\)-\(\frac{9}{5}\)
=\(\frac{45}{20}+\frac{30}{20}-\frac{36}{20}\)
=\(\frac{39}{20}\)
b) \(2\frac{2}{3}\times3\frac{1}{4}:2\frac{3}{4}\)
\(\frac{8}{3}\times\frac{13}{4}:\frac{11}{4}\)
=\(\frac{8}{3}\times\frac{13}{4}\times\frac{4}{11}\)
=\(\frac{104}{33}\)
Bài 2:
a) \(\frac{7}{9}+\frac{4}{5}+\frac{11}{9}+\frac{6}{5}\)
=\(\left(\frac{7}{9}+\frac{11}{9}\right)+\left(\frac{4}{5}+\frac{6}{5}\right)\)
=2+2
=4
b) \(\frac{21}{36}\times\frac{39}{14}\times\frac{54}{13}\)
=\(\frac{21\times39\times54}{36\times14\times13}\)
=\(\frac{675}{100}\)
C
3 tháng 2 2019
Đặt \(B=1+\frac{1}{3}+\frac{1}{5}+...+\frac{1}{97}+\frac{1}{99}\)
\(=\left(1+\frac{1}{99}\right)+\left(\frac{1}{3}+\frac{1}{97}\right)+\left(\frac{1}{5}+\frac{1}{95}\right)+...+\left(\frac{1}{49}+\frac{1}{51}\right)\)
\(=\frac{100}{99}+\frac{100}{3\times97}+\frac{100}{5\times95}+...+\frac{100}{49\times51}\)
\(=100\left(\frac{1}{99}+\frac{1}{3\times97}+\frac{1}{5\times95}+...+\frac{1}{49\times51}\right)\)
Đặt \(C=\frac{1}{1\times99}+\frac{1}{3\times97}+\frac{1}{5\times95}+...+\frac{1}{97\times3}+\frac{1}{99\times1}\)
\(=2\left(\frac{1}{99}+\frac{1}{3\times97}+\frac{1}{5\times95}+...+\frac{1}{49\times51}\right)\)
\(A=\frac{B}{6}=\frac{100}{2}=50\)
Vậy \(A=50\)
31 tháng 7 2023
\(\dfrac{3}{25}=\dfrac{3\times4}{25\times4}=\dfrac{12}{100}\\ \dfrac{7}{8}=\dfrac{7\times125}{8\times125}=\dfrac{875}{1000}\\ \dfrac{9}{45}=\dfrac{9:9}{45:9}=\dfrac{1}{5}=\dfrac{1\times2}{5\times2}=\dfrac{2}{10}\)
22 tháng 4 2019
\(\left|\frac{2}{3}x-\frac{3}{4}\right|-\frac{1}{4}=0\)
\(\Rightarrow\left|\frac{2}{3}x-\frac{3}{4}\right|=0+\frac{1}{4}\)
\(\Rightarrow\left|\frac{2}{3}x-\frac{3}{4}\right|=\frac{1}{4}\)
\(\Rightarrow\hept{\begin{cases}\frac{2}{3}x-\frac{3}{4}=\frac{1}{4}\\\frac{2}{3}x-\frac{3}{4}=-\frac{1}{4}\end{cases}}\Rightarrow\hept{\begin{cases}x=\frac{3}{2}\\x=\frac{3}{4}\end{cases}}\)
Vậy : \(x\in\left\{\frac{3}{2};\frac{3}{4}\right\}\)
20 tháng 4 2017
\(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}\)
\(=1-\left(\frac{1}{2}-\frac{1}{2}\right)-\left(\frac{1}{3}-\frac{1}{3}\right)-......-\left(\frac{1}{6}-\frac{1}{6}\right)-\frac{1}{7}\)
\(=1-\frac{1}{7}\)
\(=\frac{6}{7}\)
BM
20 tháng 4 2017
1/2+1/6+1/12+1/20+1/30+1/42
=1/1x2+1/2x3+1/3x4+1/4x5+1/5x6+1/6x7
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7
=1-1/7
=6/7
\(1+\frac{1}{1+\frac{1}{1+\frac{1}{1+\frac{1}{3}}}}=1+\frac{1}{1+\frac{1}{1+\frac{1}{\frac{4}{3}}}}=1+\frac{1}{1+\frac{1}{1+\frac{3}{4}}}=1+\frac{1}{1+\frac{1}{\frac{7}{4}}}=1+\frac{1}{1+\frac{4}{7}}=1+\frac{1}{\frac{11}{7}}=1+\frac{7}{11}=\frac{18}{11}\)