N2022 P2 Q1

N2022 P2 Q1

Junior College 2
4 marks
Free

Use the substitution \(u=\sqrt{x+2}\) to find \(\int\frac{x}{\sqrt{x+2}}\,\mathrm{d}x\).[4]

Default solution

\(u=\sqrt{x+2}\Rightarrow x=u^2-2,\quad \mathrm{d}x=2u\,\mathrm{d}u\)

\(\int\frac{x}{\sqrt{x+2}}\,\mathrm{d}x=\int 2(u^2-2)\,\mathrm{d}u\)

\(=\frac{2}{3}u^3-4u+C\)

\(=\frac{2}{3}(x+2)^{3/2}-4\sqrt{x+2}+C\)

Answer:\(\frac{2}{3}(x+2)^{3/2}-4\sqrt{x+2}+C\)

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