Question 401079
This equation will not factor so we must use the Quadratic Formula (or complete the square):
{{{x = (-(-18) +- sqrt((-18)^2 - 4(1)(-4)))/2(1)}}}
which simplifies as follows:
{{{x = (-(-18) +- sqrt(324 - 4(1)(-4)))/2(1)}}}
{{{x = (-(-18) +- sqrt(324 + 16))/2(1)}}}
{{{x = (-(-18) +- sqrt(340))/2(1)}}}
{{{x = (18 +- sqrt(340))/2}}}
{{{x = (18 +- sqrt(4*85))/2}}}
{{{x = (18 +- sqrt(4)*sqrt(85))/2}}}
{{{x = (18 +- 2*sqrt(85))/2}}}
{{{x = (2(9 +- sqrt(85)))/2}}}
{{{x = (cross(2)(9 +- sqrt(85)))/cross(2)}}}
{{{x = 9 +- sqrt(85)}}}
In long form this is:
{{{x = 9 + sqrt(85)}}} or {{{x = 9 - sqrt(85)}}}