Question 476214
{{{ e^(2x) - 3e^x - 40 = 0 }}}
Let {{{t=e^x}}} {{{t>0}}}
{{{t^2-3t-40=0}}}
{{{(t-8)(t+5)=0}}}
{{{t-8=0}}} or {{{t+5=0}}}
{{{t=8}}} or {{{t=-5<0}}} exteraneous root
{{{e^x=8}}} 
{{{x=ln8}}}