Question 668118
x^4 − 7x^2 − 144 = 0 
use the quadratic formula
{{{x^2 = (-(-7) +- sqrt(-7^2-4*1*-144 ))/(2*1) }}}
:
{{{x^2 = (7 +- sqrt(49+576 ))/2 }}}
:
{{{x^2 = (7 +- sqrt(625 ))/2) }}} 
two solutions
{{{x^2 = (7 + 25)/2 }}}
x^2 = {{{32/2}}}
x^2 = 16
x = +4, -4
and
{{{x^2 = (7 - 25)/2 }}}
x^2 = {{{-18/2}}}
Non-real solutions
:
Real solutions: x=4, x=-4