1.18: Chain rule and integration by recognition

0606/11/O/N/18 — Question 8 · 8 marks

(i)
Find ddx(5x2+4)32\dfrac{\mathrm{d}}{\mathrm{d}x}(5x^{2} + 4)^{\frac{3}{2}}.
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(ii)
Hence find x(5x2+4)12dx\displaystyle\int x(5x^{2} + 4)^{\frac{1}{2}}\,\mathrm{d}x.
[2]
(iii)
Given that 0ax(5x2+4)12dx=1915\displaystyle\int_{0}^{a} x(5x^{2} + 4)^{\frac{1}{2}}\,\mathrm{d}x = \dfrac{19}{15}, find the value of the positive constant aa.
[4]