Question

Answer 1

`B = 4/(5.7)+4/(7.9)+4/(9.11)+.....+4/(41.43)+4/(43.45)`

`B=2.(2/(5.7)+2/(7.9)+2/(9.11)+.....+2/(41.43)+2/(43.45))`

`B=2.(1/5-1/7+1/7-1/9+.....+1/43-1/45)`

`B=2.(1/5-1/45)`

`B=2.8/45`

`B=16/45`

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Answer 2

`B=4/(5*7) + 4/(7*9) + 4/(9*11) + ... + 4/(41*43) + 4/(43*45)`

`B= 2*(2/(5*7) + 2/(7*9) + 2/(9*11) + ... + 2/(41*43) + 2/(43*45))`

`B= 2*(1/5 - 1/7 + 1/7 - 1/9 + 1/9 - 1/11 + ... + 1/41 - 1/43 +1/43 - 1/45)`

`B= 2*(1/5-1/45)`

`B= 2*(9/45 - 1/45)`

`B= 2* 8/45`

`B= 2/1 * 8/45`

`B= (2*8)/(1*45)`

`B= 16/45`