$A=\genfrac{}{}{0ex}{}{7^2}{2.9}+\genfrac{}{}{0ex}{}{7^2}{9.16}+\genfrac{}{}{0ex}{}{7}{16.23}+.....+\genfrac{}{}{0ex}{}{7^2}{65.72}$

=$7.\left(\genfrac{}{}{0ex}{}{1}{2}-\genfrac{}{}{0ex}{}{1}{9}+\genfrac{}{}{0ex}{}{1}{9}-\genfrac{}{}{0ex}{}{1}{16}+\genfrac{}{}{0ex}{}{1}{16}-\genfrac{}{}{0ex}{}{1}{23}+....+\genfrac{}{}{0ex}{}{1}{65}-\genfrac{}{}{0ex}{}{1}{72}\right)$

=$7.\left(\genfrac{}{}{0ex}{}{1}{2}-\genfrac{}{}{0ex}{}{1}{72}\right)$

=$7.\genfrac{}{}{0ex}{}{35}{72}$

=$\genfrac{}{}{0ex}{}{245}{72}$
 

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

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