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ai nhanh giup minh di roi minh cho nick "lien quan mobile" rank vang
B=1/16+ 6/16.26+ 6/26.36+ ..................+ 6/2006.2016
B=1/16+ 6. (1/16.26+ 1/26.36 +.................+ 1/2006.2016)
10B=1/16+6.(1/16- 1/2016)
10B=7.1/16 - 1/336
10B=7/16 - 1/336
10B=73/168
B=73/1680
làm hơi tắt bạn cố hiểu nhé
\(B=\frac{1}{16}+\frac{6}{16.26}+\frac{6}{26.36}+\frac{6}{36.46}+...+\frac{6}{2006.2016}\) =\(B=\frac{1}{16}+\frac{3}{5}\left(\frac{10}{16.26}+\frac{10}{26.36}+\frac{10}{36.46}+...+\frac{10}{2006.2016}\right)\)
\(B=\frac{1}{16}+\frac{3}{5}\left(\frac{1}{16}-\frac{1}{26}+\frac{1}{26}-\frac{1}{36}+\frac{1}{36}-\frac{1}{46}+...+\frac{1}{2006}-\frac{1}{2016}\right)\)
\(B=\frac{1}{16}+\frac{3}{5}\left(\frac{1}{16}-\frac{1}{2016}\right)\)
đến đây thì ổn rồi
x-y-z=0=>x=y+z
=>z=x-y;=>y=x-z
\(=>B=\left(1-\frac{z}{x}\right)\left(1-\frac{x}{y}\right)\left(1-\frac{y}{z}\right)=\left(1-\frac{x-y}{x}\right)\cdot\left(1-\frac{y+z}{y}\right)\cdot\left(1+\frac{x-z}{z}\right)\)
Câu a cậu ghi sai đầu bài rồi hay sao í! phải là \(\frac{6}{36.46}\) chứ
Bạn ơi, nếu tính bằng máy tính thì kết quả là 5/7 và bâyh mình đang cần cách giải bạn ạ
A = \(\frac{1}{3}+\frac{13}{35}+\frac{33}{35}+\frac{61}{63}+\frac{97}{99}+\frac{141}{143}\)
\(=\left(1-\frac{2}{3}\right)+\left(1-\frac{2}{15}\right)+\left(1-\frac{2}{35}\right)+\left(1-\frac{2}{63}\right)+\left(1-\frac{2}{99}\right)+\left(1-\frac{2}{143}\right)\)
\(=\left(1+1+1+1+1+1\right)-\left(\frac{2}{3}+\frac{2}{15}+\frac{2}{35}+\frac{2}{63}+\frac{2}{99}+\frac{2}{143}\right)\)
\(=6-\left(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}+\frac{2}{11.13}\right)\)
\(=6-\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+\frac{1}{11}-\frac{1}{13}\right)\)
\(=6-\left(1-\frac{1}{13}\right)\)
\(=6-1+\frac{1}{13}\)
\(=5+\frac{1}{13}\)
\(=\frac{66}{13}\)
\(\text{Vậy }A=\frac{66}{13}\)
Ta có: \(A=\frac{3-2}{3}+\frac{15-2}{15}+\frac{35-2}{35}+\frac{63-2}{63}+\frac{99-2}{99}+\frac{143-2}{143}+\frac{195-2}{195}\)
\(A=\left(1-\frac{2}{3}\right)+\left(1-\frac{2}{15}\right)+\left(1-\frac{2}{35}\right)+\left(1-\frac{2}{63}\right)+\left(1-\frac{2}{99}\right)+\left(1-\frac{2}{143}\right)+\left(1-\frac{2}{195}\right)\)
\(A=7-\left(\frac{2}{3}+\frac{2}{15}+\frac{2}{35}+\frac{2}{63}+\frac{2}{99}+\frac{2}{143}+\frac{2}{195}\right)\)
\(A=7-\left(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}+\frac{2}{11.13}+\frac{2}{13.15}\right)\)
\(A=7-\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}\right)\)
\(A=7-\left(1-\frac{1}{15}\right)=7-1+\frac{1}{15}=6\frac{1}{15}\)không là số nguyên
\(B=\frac{1}{16}+\frac{6}{16.26}+\frac{6}{26.36}+....+\frac{6}{2006.2016}\)
\(=\frac{6}{6.16}+\frac{6}{16.26}+\frac{6}{26.36}+....+\frac{6}{2006.2016}\)
\(=\frac{6}{10}\left(\frac{1}{6}-\frac{1}{16}+\frac{1}{16}-\frac{1}{26}+...+\frac{1}{2006}-\frac{1}{2016}\right)\)
\(=\frac{3}{5}\left(\frac{1}{6}-\frac{1}{2016}\right)\)
\(=\frac{67}{672}\)
\(B=\frac{1}{16}+\frac{6}{16\cdot26}+\frac{6}{26\cdot36}+...+\frac{6}{2006\cdot2016}\)
\(B=\frac{1}{16}+6\left(\frac{1}{16\cdot26}+\frac{1}{26\cdot36}+...+\frac{1}{2006\cdot2016}\right)\)
\(B=\frac{1}{16}+6\left[\frac{1}{10}\left(\frac{10}{16\cdot26}+\frac{10}{26\cdot36}+...+\frac{10}{2006\cdot1016}\right)\right]\)
\(B=\frac{1}{16}+6\left[\frac{1}{10}\left(\frac{1}{16}-\frac{1}{26}+\frac{1}{26}-\frac{1}{36}+...+\frac{1}{2006}-\frac{1}{2016}\right)\right]\)
\(B=\frac{1}{16}+6\left[\frac{1}{10}\left(\frac{1}{16}-\frac{1}{2016}\right)\right]\)
\(B=\frac{1}{16}+6\cdot\left[\frac{1}{10}\cdot\frac{125}{2016}\right]\)
\(B=\frac{1}{16}+6\cdot\frac{26}{4032}\)
\(B=\frac{1}{16}+\frac{25}{672}\)
\(B=\frac{57}{672}\)
Ta có: \(G=\frac{2}{15}+\frac{2}{35}+\frac{2}{63}+...+\frac{2}{399}\)
\(=\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{19}-\frac{1}{21}=\frac{1}{3}-\frac{1}{21}=\frac{2}{7}\)
\(\frac{\frac{15}{6.16}+\frac{15}{16.26}+\frac{15}{26.36}}{\frac{33}{6.16}-\frac{63}{16.26}-\frac{93}{26.36}}\)
\(=\frac{\frac{15}{10}\cdot\left(\frac{1}{6}-\frac{1}{16}+\frac{1}{16}-\frac{1}{26}+\frac{1}{26}-\frac{1}{36}\right)}{\frac{11}{32}-\frac{63}{416}-\frac{31}{312}}\)
\(=\frac{\frac{15}{10}\cdot\left(\frac{1}{6}-\frac{1}{36}\right)}{\frac{143}{416}-\frac{63}{416}-\frac{124}{\frac{3}{416}}}=\frac{\frac{5}{24}}{\frac{143-63-\frac{124}{3}}{416}}\)
\(=\frac{\frac{5}{24}}{\frac{116}{\frac{3}{416}}}=\frac{\frac{5}{24}}{\frac{29}{312}}=\frac{65}{29}\)
phần cuối là trừ hết nhá mình bấm nhầm