Apply the quadratic formula to $3x^2+2x+5=0$. What do you get?

$D=b^2-4ac=2^2-4(3)(5)=4-60=-56$. Since $D<0,\sqrt{D}$ is not a real number, so the equation has no real roots. (Writing $b^2+4ac$ would give 64 — a common slip.)