Question 411649
x2/3 - 2x1/3 - 15 = 0 
{{{(x^2)}}}1/3 - 2x1/3 - 15 = 0
Let x1/3=u 
Therefore the equation is {{{u^2-2u-15=0}}}
{{{u^2+3u-5u-15=0}}}
{{{u(u+3)-5(u+3)=0}}}
{{{(u-5)(u+3)=0}}}
{{{u-5=0}}}  or  {{{u+3=0}}}
{{{u=5}}}  or  {{{u=-3}}}