\(S=\frac{5^2}{1.6}+\frac{5^2}{6.11}+...+\frac{5^2}{26.31}\)
\(S=5.\left(\frac{5}{1.6}+\frac{5}{6.11}+...+\frac{5}{26.31}\right)\)
\(S=5.\left(1-\frac{1}{6}+\frac{1}{6}-\frac{1}{11}+...+\frac{1}{26}-\frac{1}{31}\right)\)
\(S=5.\left(1-\frac{1}{31}\right)\)
\(S=5.\frac{30}{31}\)
\(S=\frac{150}{31}\)
Câu L bạn thiếu số\(\frac{1}{475}\)
\(L=\frac{1}{7}+\frac{1}{91}+\frac{1}{247}+\frac{1}{475}+\frac{1}{775}+\frac{1}{1147}\)
\(L=\frac{1}{1.7}+\frac{1}{7.13}+\frac{1}{13.19}+\frac{1}{19.25}+\frac{1}{25.31}+\frac{1}{31.37}\)
\(L=\frac{1}{6}.\left(\frac{6}{1.7}+\frac{6}{7.13}+\frac{6}{13.19}+\frac{6}{19.25}+\frac{6}{25.31}+\frac{6}{31.37}\right)\)
\(L=\frac{1}{6}.\left(1-\frac{1}{7}+\frac{1}{7}-\frac{1}{13}+\frac{1}{13}-\frac{1}{19}+\frac{1}{19}-\frac{1}{25}+\frac{1}{25}-\frac{1}{31}+\frac{1}{31}-\frac{1}{37}\right)\)
\(L=\frac{1}{6}.\left(1-\frac{1}{37}\right)\)
\(L=\frac{1}{6}.\frac{36}{37}\)
\(L=\frac{6}{37}\)
\(S=\frac{5^2}{1.6}+\frac{5^2}{6.11}+...+\frac{5^2}{26.31}\)
\(=5\left[\left(1-\frac{1}{6}\right)+\left(\frac{1}{6}-\frac{1}{11}\right)+...+\left(\frac{1}{26}-\frac{1}{31}\right)\right]\)
\(=5\left[1-\frac{1}{31}\right]\)
\(=5.\frac{30}{31}=\frac{150}{31}\)
\(L=\frac{1}{7}+\frac{1}{91}+\frac{1}{247}+\frac{1}{775}+\frac{1}{1147}\)
\(L.6=\frac{6}{1.7}+\frac{6}{7.13}+\frac{6}{13.19}+\frac{6}{19.25}+\frac{6}{25.31}\)
\(L.6=\left(1-\frac{1}{7}\right)+\left(\frac{1}{7}-\frac{1}{13}\right)+\left(\frac{1}{13}-\frac{1}{19}\right)+\left(\frac{1}{19}-\frac{1}{25}\right)+\left(\frac{1}{25}-\frac{1}{31}\right)\)
\(L.6=1-\frac{1}{31}\)
\(L.6=\frac{31}{31}-\frac{1}{31}\)
\(L.6=\frac{25}{31}\)
\(L=\frac{30}{31}:6\)
\(L=\frac{30}{31}.\frac{1}{6}\)
\(L=\frac{30}{186}\)
S=5*5/1*6 + 5*5/6*11+...+5*5/26*31
S=5*(5/1*6+5/6*11+...+5/26*31)
S=5*(1-1/6+1/6-1/11+...+1/26-1/31)
S=5*(1-1/31)
S=5*30/31
S=150/31
Vậy S=150/31
a, \(s=5\cdot\left(\frac{5}{1\cdot6}+\frac{5}{6\cdot11}+......+\frac{5}{26\cdot31}\right)\\ s=5\cdot\left(1-\frac{1}{6}+\frac{1}{6}-\frac{1}{11}+....+\frac{1}{26}-\frac{1}{31}\right)\)\(S=5\cdot\left(1-\frac{1}{31}\right)\\ S=5\cdot\frac{30}{31}=4\frac{26}{31}\)
\(S=\frac{5^2}{1.6}+\frac{5^2}{6.11}+...+\frac{5^2}{26.31}\)
\(S=5\left(\frac{5}{1.6}+\frac{5}{6.11}+...+\frac{5}{26.31}\right)\)
\(S=5\left(1-\frac{1}{6}+\frac{1}{6}+\frac{1}{11}+...+\frac{1}{26}-\frac{1}{31}\right)\)
\(S=5\left(1-\frac{1}{31}\right)\)
\(S=5.\frac{30}{31}\)
\(S=\frac{150}{31}\)
\(L=\frac{1}{7}+\frac{1}{91}+\frac{1}{247}+...+\frac{1}{775}+\frac{1}{1147}\)(MK NGHĨ ĐỀ BỊ THIẾU)
\(6L=\frac{6}{7}+\frac{6}{91}+\frac{6}{241}+...+\frac{6}{775}+\frac{6}{1147}\)
\(6L=\frac{6}{1.7}+\frac{6}{7.13}+\frac{6}{13.19}+...+\frac{6}{25.31}+\frac{6}{31.37}\)
\(6L=1-\frac{1}{7}+\frac{1}{7}-\frac{1}{13}+\frac{1}{13}-\frac{1}{19}+...+\frac{1}{25}-\frac{1}{31}+\frac{1}{31}-\frac{1}{37}\)
\(6L=1-\frac{1}{37}\)
\(6L=\frac{36}{37}\)
\(L=\frac{36}{37}:6\)
\(L=\frac{6}{37}\)
S=521.6 +526.11 +...+5226.31
=5[(1−16 )+(16 −111 )+...+(126 −131 )]
=5[1−131 ]
=5.3031 =15031
L=17 +191 +1247 +1775 +11147
L.6=61.7 +67.13 +613.19 +619.25 +625.31
L.6=(1−17 )+(17 −113 )+(113 −119 )+(119 −125 )+(125 −131 )
L.6=1−131
L.6=3131 −131
L.6=2531
L=3031 :6
L=3031 .16
L=30186
