Question 707545
{{{x^2-2x-13=0}}}
a=1
b=-2
c=-13

Using quadratic formula:
{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}
={{{x = (-(-2) +- sqrt( (-2)^2-4*(1)*(-13) ))/(2*(1)) }}}
={{{x = (2 +- sqrt( 4-(-52) ))/(2) }}}
={{{x = (2 +- sqrt( 4+52 ))/(2) }}}
={{{x = (2 +- sqrt( 56 ))/(2) }}}

Positive square root:
={{{x = (2 + sqrt( 56 ))/(2) }}}
={{{x = (2 + 2sqrt( 14 ))/(2) }}}
={{{x = (1 + sqrt( 14 )) }}}


Negative square root:
={{{x = (2 - sqrt( 56 ))/(2) }}}
={{{x = (2 - 2sqrt( 14 ))/(2) }}}
={{{x = (1 - sqrt( 14 )) }}}