Question 136276
2x^2+x=21
2x^2+x-21=0
{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}} 
x=(-1+-sqrt(1^2-4*2*-21])/2*2
x=(-1+-sqrt[1+168])/4
x=(-1+-sqrt169)/4
x=(-1+-13)/4
x=(-1+13/4
x=12/4
x=3 answer.
x=(-1-13)/4
x=(-14)/4
x=-3.5 answer.