1.

`int_(8)^(15)(dx)/((x-3)sqrt(x+1))` is equal toA. `(1)/(2)log.(5)/(3)`B. `(1)/(3)log.(5)/(3)`C. `(1)/(5)log.(3)/(5)`D. `(1)/(2)log.(3)/(5)`

Answer» Correct Answer - A
Put `x +1 = t^(2) rArr dx = 2t dt `
At x= 8, t=3 and x=15 , t =4
` :. l = int_(3)^(4) (2t dt)/((t^(2)-1-3)t)` ,
` = int _(3) ^(4) (2dt)/((t^(2)-4))= 2. 1/4 [log. (t-2)/(t+2)]_(3)^(4)`
` = 1/2 [ log. 1/3 - log. 1/5] =1/2 log. 5/3`


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