Question 84685
Solve using the quadratic formula: {{{x = (-b+-sqrt(b^2-4ac))/2a}}}
{{{2x^2+x-1 = 0}}} Here, a = 2, b = 1, and c = -1 So, making the appropriate substitutions, we get:
{{{x = (-1+-sqrt(1^2-4(2)(-1)))/2(2)}}} Now simplify this.
{{{x = (-1+-sqrt(1+8))/4}}}
{{{x = (-1+-sqrt(9))/4}}}
{{{x = (-1+3)/4}}} or {{{x = (-1-3)/4}}}
{{{x = 1/2}}} or {{{x = -1}}} Note the negative on the 1.