Question 4386
{{{x^4 - 3x^2 - 10 = 0}}}

Let {{{u = x^2}}}, which means that {{{u^2 = x^4}}}


Substitute these into the original equation to obtain:
{{{u^2 - 3u - 10 = 0}}}, which can be factored into
{{{(u-5)(u+2)=0}}}


Solve for u, and get 
{{{u = 5}}}   or   {{{u=-2}}}


Next substitute back into {{{u = x^2}}}
{{{u = 5}}}   or   {{{u=-2}}}
{{{x^2 = 5}}} or  {{{x^2 = -2}}}


Are you solving for real solutions or do you need all real or complex solutions?  Either way, take square root of each side of both equations.


First equation:
{{{x^2 = 5}}}  
{{{x = sqrt (5)}}} or {{{x = -sqrt (5)}}}


Second equation:
{{{x^2 = -2}}}

{{{x = sqrt (-2)}}} or {{{x = -sqrt (-2)}}}
{{{x = i * sqrt (2)}}} or {{{x = - i*sqrt (2)}}}


R^2 at SCC