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What is `int(dx)/(x(x^7+1))` equal to?A. `(1)/(2) ln |(x^(7) -1)/(x^(7) + 1)| + c`B. `(1)/(7) ln |(x^(7) + 1)/(x^(7))| +_c`C. `ln |(x^(7) -1)/(7x)| +c`D. `(1)/(7) ln |(x^(7))/(x^(7) + 1)| + c` |
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Answer» Correct Answer - D `int (dx)/(x(x^(7) + 1)) = int (x^(6))/(x^(7)(x^(7) + 1)).dx` Let `x^(7) = t` `rArr 7x^(6).dx = dt rArr x^(6) dx = (dt)/(7)` Then `int (x^(6) dx)/(x^(7) (x^(7)+ 1)) = (1)/(7) int (dt)/(t(t + 1))` `= (1)/(7) [int (1)/(t) dt - int (1)/(t + 1) dt]` `= (1)/(7)[l n |t| - l n |t + 1|] + c` `= (1)/(7) l n |(t)/(t + 1)| + c` `= (1)/(7) l n |(x^(7))/(x^(7) + 1)| + c` |
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