Question 1090596
Substitute {{{u=x^2}}},
{{{x^4-6x^2+5=u^2-6u+5}}}
{{{x^4-6x^2+5=(u-5)(u-1)}}}
{{{x^4-6x^2+5=(x^2-5)(x^2-1)}}}
{{{x^4-6x^2+5=(x-sqrt(5))(x+sqrt(5))(x-1)(x+1)}}}
Not sure what you mean by the sum of the factors,
{{{x-sqrt(5)+x+sqrt(5)+x-1+x+1=4x}}}
or
{{{sqrt(5)-sqrt(5)+1-1=0}}}