\(A=\frac{7}{4}.\left(\frac{3333}{1212}+\frac{3333}{2020}+\frac{3333}{3030}+\frac{3333}{4242}\right)\)

\(A=\frac{7}{4}.\left(\frac{33.101}{12.101}+\frac{33.101}{20.101}+\frac{33.101}{30.101}+\frac{33.101}{42.101}\right)\)

\(A=\frac{7}{4}.\left(\frac{33}{12}+\frac{33}{20}+\frac{33}{30}+\frac{33}{42}\right)\)

\(A=\frac{7.11}{4}.\left(\frac{1}{4}+\frac{3}{20}+\frac{1}{10}+\frac{1}{14}\right)\)

\(A=\frac{77}{4}.\left(\frac{35}{140}+\frac{21}{140}+\frac{14}{140}+\frac{10}{140}\right)\)

\(A=\frac{77}{4}.\frac{80}{140}=\frac{77}{8}.\frac{20}{35}\)

\(A=11\)

Vậy : \(A=11\)

A = 7/4 * ( 3333/1212 + 3333/2020 + 3333/3030 + 3333/4242)                                  => A = 7/4* (33/12 + 33/20 + 33/30 + 33/42)                                                              => A = 7/4* ( 33/3*4 + 33/4*5 + 33/5*6 + 33/6*7)                                                        => A = 7/4* { 33/(4-3) * ( 1/4 - 1/5 + 1/5 - 1/6 + 1/6-1/7)}                                              => A = 7/4*33 * ( 1/4 - 1/7)                                                                                                A = 231/4 * 3/28 =693/112.

A=7/4.(3333/1212+3333/2020+3333/3030+3333/4242)

A=7/4 X 44/7

A=11

rút gọn: B= ( 1-1/2). ( 1-1/3). (1-1/4).....(1-1/20)

\(\frac{7}{4}\left(\frac{3333}{1212}+\frac{3333}{2020}+\frac{3333}{3030}+\frac{3333}{4242}\right)=\frac{7}{4}\left(\frac{33\times101}{12\times101}+\frac{33\times101}{20\times101}+\frac{33\times101}{30\times101}+\frac{33\times101}{42\times101}\right)\)

\(=\frac{7}{4}\left(\frac{33}{12}+\frac{33}{20}+\frac{33}{30}+\frac{33}{42}\right)=\frac{7}{4}\times\frac{44}{7}=11\)

A = 7/4.[3333.(1/1212+1/2020+1/3030+1/4242)]

A= 7/4.[3333.(1/12.101+1/20.101+1/30.101+1/42.101)]

A= 7/4.[3333.(1/12+1/20+1/30+1/42)]

A= 7/4.[3333.(1/3.4+1/4.5+1/5.6+1/6.7)]

A= 7/4.[3333.(1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7)]

A= 7/4.[3333.(1/3-1/7)]

A= 7/4.[3333.4/21]

A= 7/4.4444/7

A=1111

\(A=\frac{7}{4}\left(\frac{11}{4}+\frac{33}{20}+\frac{11}{10}+\frac{11}{14}\right)\)

\(A=\frac{7}{4}.\frac{44}{7}=11\)

chuẩn ròi

\(A=\frac{7}{4}.\left(\frac{3333}{1212}+\frac{3333}{2020}+\frac{3333}{3030}+\frac{3333}{4242}\right)\)

\(A=\frac{7}{4}.\left(\frac{33}{12}+\frac{33}{20}+\frac{33}{30}+\frac{33}{42}\right)\)

\(A=\frac{7}{4}.33.\left(\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}\right)\)

\(A=\frac{231}{4}.\left(\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}\right)\)

\(A=\frac{231}{4}.\left(\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}\right)\)

\(A=\frac{231}{4}.\left(\frac{1}{3}-\frac{1}{7}\right)\)

\(A=\frac{231}{4}.\frac{4}{21}\)
\(A=11\)

A = 11 nha !