Question

[Phương Anh _1348]

A= 1/1.4 + 1/4.7 + 1/7.10 +......+ 1/94.97

Em cần gấp mn ơi

Answer 1

[chuyên toán thcs ( Cool Team )]

\(=\frac{1}{3}\left(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{94.97}\right).\)

\(=\frac{1}{3}\left(\frac{1}{1}-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+...+\frac{1}{94}-\frac{1}{97}\right)\)

\(=\frac{1}{3}\left(\frac{1}{1}-\frac{1}{97}\right)\)

\(=\frac{1}{3}.\frac{96}{97}\)

\(=\frac{32}{97}\)

học tốt 

Answer 2

[HotBoy Cô Đơn]

3A = 3(1/1.4 + 1/4.7 + 1/7.10 + ...... + 1/94.97)

3A=1 - 1/4 + 1/4 - 1/7 + 1/7 - 1/10 + 1/10 - ........ - 1/97

3A = 1-1/97

3A = 96/97

A = 32/97

Oke nha bạn