Question
Evaluate $\int_{-1}^{1} 5 x^{4} \sqrt{x^{5}+1} d x$

Answer

Put t = x5 + 1, then dt = 5x4 dx.
Therefore, $\int 5 x^{4} \sqrt{x^{5}+1} d x$ = $\int \sqrt{t} d t=\frac{2}{3} t^{\frac{3}{2}}=\frac{2}{3}\left(x^{5}+1\right)^{\frac{3}{2}}$ 
Hence, $\int_{-1}^{1} 5 x^{4} \sqrt{x^{5}+1} d x$ = $\frac{2}{3}\left[\left(x^{5}+1\right)^{\frac{3}{2}}\right]_{-1}^{1}$ 
= $\frac{2}{3}\left[\left(1^{5}+1\right)^{\frac{3}{2}}-\left((-1)^{5}+1\right)^{\frac{3}{2}}\right]$ 
= $\frac{2}{3}\left[2^{\frac{3}{2}}-0^{\frac{3}{2}}\right]=\frac{2}{3}(2 \sqrt{2})=\frac{4 \sqrt{2}}{3}$ 

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free