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\(A=\frac{4\cdot0,125\cdot20,2\cdot800\cdot0,25}{1,01\cdot75+0,26\cdot101-1,01}\)
\(=\frac{4\cdot0,25\cdot0,125\cdot800\cdot20,2}{1,01\cdot75+0,26\cdot100\cdot1,01-1,01}\)
\(=\frac{1\cdot100\cdot20,2}{1,01\cdot\left(75+26-1\right)}\)
\(=\frac{100\cdot20,2}{100\cdot1,01}\)
= 20
\(B=\left(\frac{178}{179}+\frac{179}{180}+\frac{180}{181}\right)\cdot\left(\frac{80}{56}-\frac{15}{12}:\frac{7}{8}\right)\)
\(=\left(\frac{178}{179}+\frac{179}{180}+\frac{180}{181}\right)\cdot\left(\frac{10}{7}-\frac{5}{4}\cdot\frac{8}{7}\right)\)
\(=\left(\frac{178}{179}+\frac{179}{180}+\frac{180}{181}\right)\cdot\left(\frac{10}{7}-\frac{10}{7}\right)\)
\(=\left(\frac{178}{179}+\frac{179}{180}+\frac{180}{181}\right)\cdot0\)
= 0
\(A=\frac{65+891+135+909}{731-47+69-253}\)
\(A=\frac{65+135+891+909}{731+69-47-253}\)
\(A=\frac{\left(65+135\right)+\left(891+909\right)}{\left(731+69\right)-\left(47+253\right)}\)
\(A=\frac{200+1800}{800-300}\)
\(A=\frac{2000}{500}=4\)
A = \(\frac{65+891+135+909}{731-47+69-253}\)
A = \(\frac{\left(65+135\right)+\left(891+909\right)}{\left(731+69\right)-\left(47+253\right)}\)
A = \(\frac{200+1800}{800-300}\)
A = \(\frac{2000}{500}\)
A = 4
\(=1\left(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{9.10}\right)\)
\(=1\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-...+\frac{1}{9}-\frac{1}{10}\right)\)
\(=1-\frac{1}{10}\)
\(=\frac{9}{10}\)
\(\frac{2}{1.2}+\frac{2}{2.3}+\frac{2}{3.4}+....+\frac{2}{19.20}\)
\(=2.\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+....+\frac{1}{19.20}\right)\)
\(=2.\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+....+\frac{1}{19}-\frac{1}{20}\right)\)
\(=2.\left(1-\frac{1}{20}\right)\)
\(=2.\frac{19}{20}=\frac{19}{10}\)
\(\frac{1}{2}\)+ \(\frac{1}{4}\) + \(\frac{1}{8}\) + \(\frac{1}{16}\) + \(\frac{1}{32}\)
= [ 1 - \(\frac{1}{2}\)] + [ \(\frac{1}{2}\) - \(\frac{1}{4}\)] + [ \(\frac{1}{4}\) - \(\frac{1}{8}\)] + [ \(\frac{1}{8}\) - \(\frac{1}{16}\)] + [ \(\frac{1}{16}\) - \(\frac{1}{32}\)]
Xóa bỏ các phân số trùng lặp , ta được tổng của dãy số là :
1 - \(\frac{1}{32}\) = \(\frac{31}{32}\)
Đ/S :\(\frac{31}{32}\)