2.35: Product rule and logarithmic integration

0606/22/M/J/17 — Question 5 · 5 marks

(i)
Show that ddx[0.4x5(0.2ln5x)]=kx4ln5x\dfrac{\mathrm{d}}{\mathrm{d}x}\bigl[0.4x^{5}(0.2 - \ln 5x)\bigr] = kx^{4}\ln 5x, where kk is an integer to be found.
[2]
(ii)
Express ln125x3\ln 125x^{3} in terms of ln5x\ln 5x.
[1]
(iii)
Hence find (x4ln125x3)dx\displaystyle\int (x^{4}\ln 125x^{3})\,\mathrm{d}x.
[2]