2.49: Differentiating and integrating lnx\ln x

0606/22/O/N/17 — Question 9 · 8 marks

(i)
Find ddx(xlnx)\dfrac{\mathrm{d}}{\mathrm{d}x}(x\ln x).
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(ii)
Hence find lnxdx\displaystyle\int \ln x\,\mathrm{d}x.
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(iii)
Hence, given that k>0k > 0, show that k2klnxdx=k(ln4k1)\displaystyle\int_{k}^{2k} \ln x\,\mathrm{d}x = k(\ln 4k - 1).
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