Question

Factor 3x^2-20x-7.

Answer 1

Hi,

Without discriminant:

$3x^2-20x-7\\\\ =3(x^2-\dfrac{2*10}{3} )-7\\\\ =3(x^2-\dfrac{2*10}{3}+\dfrac{100}{9} )-\dfrac{100}{3}-7\\\\ =3(x-\dfrac{10}{3})^2-\dfrac{121}{3}\\\\ =\sqrt{3}[(x-\dfrac{10}{3})+\dfrac{11}{3}]*\sqrt{3}[(x-\dfrac{10}{3})-\dfrac{11}{3}]\\\\ =3(x+\frac{1}{3})(x-\dfrac{21}{3})\\\\ =(3x+1)(x-7)$