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a,=25/6;7/6=25/6x6/7=25/7
b,=7/2x32/6=56/3
c,=17/5-11/10=34/10-11/10=23/10
d,=8/3+11/4=32/12+33/12=65/12
a,=25/6;7/6=25/6x6/7=25/7
b,=7/2x32/6=56/3
c,=17/5-11/10=34/10-11/10=23/10
d,=8/3+11/4=32/12+33/12=65/12
a) \(x+4\frac{1}{5}=5\frac{2}{3}\times10\frac{1}{2}\)
\(x+\frac{21}{5}=\frac{17}{3}\times\frac{21}{2}\)
\(x+\frac{21}{5}=\frac{119}{2}\)
\(x=\frac{119}{2}-\frac{21}{5}\)
\(x=\frac{553}{10}\)
b) \(\frac{24}{5}-x=2\frac{1}{4}:1\frac{3}{4}\)
\(\frac{24}{5}-x=\frac{9}{4}:\frac{7}{4}\)
\(\frac{24}{5}-x=\frac{9}{4}.\frac{4}{7}\)
\(\frac{24}{5}-x=\frac{9}{7}\)
\(x=\frac{24}{5}-\frac{9}{7}\)
\(x=\frac{123}{35}\)
\(1\frac{1}{5};1\frac{1}{2};1\frac{3}{5};2\frac{1}{2};2\frac{2}{3}\)
\(\frac{1}{1+2}+\frac{1}{1+2+3}+\frac{1}{1+2+3+4}+\frac{1}{1+2+3+4+5}\)
\(=\frac{1}{1+2}\times\left(1+\frac{1}{1+2+3}\div\frac{1}{1+2}+\frac{1}{1+2+3+4}\div\frac{1}{1+2}+\frac{1}{1+2+3+4+5}\div\frac{1}{1+2}\right)\)
\(=\frac{1}{1+2}\times\left(1+\frac{1}{2}+\frac{3}{10}+\frac{1}{5}\right)\)
\(=\frac{1}{1+2}\times2\)
\(=\frac{2}{3}\)
=\(\frac{2}{3}\)
\(\frac{1}{1+2}+\frac{1}{1+2+3}+\frac{1}{1+2+3+4}+\frac{1}{1+2+3+4+5}\)
\(=\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+\frac{1}{15}\)
\(=\frac{2}{6}+\frac{2}{12}+\frac{2}{20}+\frac{2}{30}\)
\(=2.\left(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}\right)\)
\(=2.\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}\right)\)
\(=2.\left(\frac{1}{2}-\frac{1}{6}\right)\)
\(=2.\frac{1}{3}\)
\(=\frac{2}{3}\)
Dấu \(.\)là dấu nhân nha bạn
Đặt \(A=\frac{1}{1+2}+\frac{1}{1+2+3}+\frac{1}{1+2+3+4}\)\(+\frac{1}{1+2+3+4+5}\)
\(\Rightarrow\) \(A=\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+\frac{1}{15}\)
\(\Rightarrow\)\(\frac{1}{2}A=\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}\)
\(\Rightarrow\)\(\frac{1}{2}A=\frac{1}{2x3}+\frac{1}{3x4}+\frac{1}{4x5}+\frac{1}{5x6}\)
\(\Rightarrow\)\(\frac{1}{2}A=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}\)
\(\Rightarrow\)\(\frac{1}{2}A=\frac{1}{2}-\frac{1}{6}\)
\(\Rightarrow\)\(\frac{1}{2}A=\frac{1}{3}\)
\(\Rightarrow\) \(A=\frac{1}{3}:\frac{1}{2}\)
\(\Rightarrow\) \(A=\frac{2}{3}\)
Vậy ...
Fan Long Hoàng và Linh Ka điểm danh !