Question 364888
{{{x^2-10x-3=0}}}
When you factor, you look for factors of {{{3}}} that add to {{{10}}}.
({{{1}}},{{{3}}}) don't add to ten so you can't take that route.
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Quadratic formula always works. 
Completing the square always works too but can get involved too depending on the coefficients.
Factor if it's readily apparent what the factors are.
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{{{(x^2-10x+25)-3-25=0}}}
{{{(x-5)^2=28}}}
{{{x-5=0 +- sqrt(28)}}}
{{{highlight(x=5 +- 2*sqrt(7))}}}