(b) Put $1 + \log x = t\ \Rightarrow \ \frac{1}{x}dx = dt$ $\int_{}^{}{\frac{dx}{x\left( 1 + \log x \right)^{2}} = \int_{}^{}t^{- 2}dt = \frac{t^{- 1}}{- 1} + c = \frac{- 1}{(1 + \log x)} + c}$
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