Question 81279
R^2+16R+21=0
{{{r = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}} 
R=(-16+-SQRT[16^2-4*1*21])/2*1
R=(-16+-SQRT[256-84])/2
R=(-16+-SQRT172)/2
R=(-16+-13.11)/2
R=(-16+13.11)/2
R=-2.88/2
R=-1.44 ANSWER.
R=(-16-13.11)/2
R=-29.11/2
R=-14.555 ANSWER.