Question 357892
{{{x^4+3x^2-4=0}}}
Use a substitution,
{{{u=x^2}}}
{{{u^2=x^4}}}
{{{u^2+3u-4=0}}}
{{{(u+4)(u-1)=0}}}
{{{u+4=0}}}
{{{x^2+4=0}}}
{{{x^2=-4}}}
{{{highlight(x=0 +- 2i)}}}
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.
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{{{u-1=0}}}
{{{x^2=1}}}
{{{highlight(x=0 +- 1)}}}