I get up to about when I'm substituting in u and du, because I find that du is an unwieldy fraction and I'm not sure what to do with the x

^{3}in the top. According to the integration calculator I consulted, if u had just been (x

^{2}+1), then x

^{3}would become (u-1) (which I'm also not sure about how but is not the pressing question).

Thank you for your time!