Question 330169
x^2+18x-4=0

compare it with the general equation
ax^2 +bx +c
a=1, b=18, c=-4
x1,x2 the roots of the equation are 
{{{x1 = (-b +sqrt(b^2-4ac))/(2a)}}}
.
plug the values of a,b,c in the equation.
{{{x1=(-(18)+sqrt((18)^2-4*1*(-4)))/(2*1)}}}
{{{x1=-18+sqrt(324+16)/(2)}}}
{{{x1= (-18+sqrt(340))/(2)}}}
{{{x1=(-18+2*sqrt(85))/(2)}}}
{{{x1=(2*(-9+sqrt(85)))/2}}}
{{{x1=(-9+sqrt85)}}}
...
{{{x2=(-9-sqrt85)}}}