Question 406025
{{{x^2+x-20=0}}}
 {{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}} till here you were absolutely right
Look at formula of the quadratic equation {{{ax^2+bx+c=0}}}, a, b  are coefficients before {{{x^2}}} and {{{x}}}, c is the free term
so {{{a=1}}}, {{{b=1}}}, {{{c=-20}}}, put in formula
{{{x = (-1 +- sqrt( 1^2-4*1*(-20) ))/(2*1) }}} 
{{{x = (-1 +- sqrt( 81 ))/2 }}} 
{{{x1 = (-1 +9)/2 }}} or {{{x2 = (-1 -9)/2 }}} 
{{{x1 = 4 }}} or {{{x2 = -5}}}