Consider the standard integral of [imath]\arcsin(u)[/imath], which is
[math]\arcsin(u)=\int \frac{1}{\sqrt{1-u^2}}\,du[/math]Notice your problem resembles it (in red).
[math]\int\frac{x}{\sqrt{3-x^4}}\,dx=\int\frac{x}{\sqrt{3}\sqrt{1-\frac{x^4}{3}}}\,dx=\int\frac{x}{\sqrt{3}}\cdot \red{\frac{1}{\sqrt{1-\frac{x^4}{3}}}}\,dx[/math]If you recognized that, it's an obvious choice to make a u-subsitution [imath]u^2=\frac{x^4}{3}[/imath] or [imath]u=\frac{x^2}{\sqrt{3}}[/imath].
I'll let you work out the details but clearly, this isn't something you're expected to do and I second Dr.P's comments. It's more valuable for you.