5) (i) Use the substitution $\displaystyle u^2=2x+1$ to show that, $\displaystyle x>4$

$\displaystyle \int\frac{3}{(x-4)\sqrt{2x+1}}dx=\ln(\frac{\sqrt{2x+1}-3}{\sqrt{2x+1}+3})+K$

where K is a constant.

(ii) Show that (from ln 8 to ln 3)$\displaystyle \int\frac{2}{e^x\sqrt{e^x+1}}=\frac{7}{12}+\ln\fra c{2}{3}$

:'( hints please