This is as far as I can get...

$B\left[\left(\frac{3^{\frac{1}{\left(x-1\right)}}}{1+3^{\frac{1}{\left(x-1\right)}}}\right)^x+3\left(\frac{1}{1+3^{\frac{1}{\left(x-1\right)}}}\right)^x\right]^{\frac{1}{x}}$

I can take the B out because it is subject to the same exponent in both parts but I'm at a loss what to do now?

I should be able to get to this expression but I just can't see how - does anyone have any tips for me?

$B\cdot 3^{\frac{1}{x}}\left(1+3^{\frac{1}{\left(x-1\right)}}\right)^{\frac{1}{x}-1}$

Thanks so much!