Question

Tính \(A=\frac{7^2}{2.9}+\frac{7^2}{9.16}+\frac{7^2}{16.23}+..........+\frac{7^2}{65.72}\)

Answer 1

A = 7 (7 / 2.9 + 7 / 9.16 + .......... + 7/65.72)

A=7( 1/2 - 1/9 +1/9 - 1/16 +......+1/65 - 1/72)

A= 7 ( 1/2 -1/72)

A= 7 . 35/72

A=245/72

Answer 2

\(A=\frac{7^2}{2.9}+\frac{7^2}{9.16}+\frac{7}{16.23}+.....+\frac{7^2}{65.72}\)

=\(7.\left(\frac{1}{2}-\frac{1}{9}+\frac{1}{9}-\frac{1}{16}+\frac{1}{16}-\frac{1}{23}+....+\frac{1}{65}-\frac{1}{72}\right)\)

=\(7.\left(\frac{1}{2}-\frac{1}{72}\right)\)

=\(7.\frac{35}{72}\)

=\(\frac{245}{72}\)

Answer 3

A=7x(\(\frac{1}{2}\)-\(\frac{1}{9}\)+\(\frac{1}{9}\)-\(\frac{1}{16}\)+.....+\(\frac{1}{65}\)-\(\frac{1}{72}\))

A=7x(\(\frac{1}{2}\)-\(\frac{1}{72}\))

A=7x\(\frac{35}{42}\)

A=\(\frac{245}{72}\)

Answer 4

A = 7 (7 / 2.9 + 7 / 9.16 + .......... + 7/65.72)

A=7( 1/2 - 1/9 +1/9 - 1/16 +......+1/65 - 1/72)

A= 7 ( 1/2 -1/72)

A= 7 . 35/72

A=245/72

 

Answer 5

A=2.972​+9.1672​+16.237​+.....+65.7272​

=7.(12−19+19−116+116−123+....+165−172)7.(21​−91​+91​−161​+161​−231​+....+651​−721​)

=7.(12−172)7.(21​−721​)

=7.35727.7235​

=2457272245​