Question

Which is the correct form of the quadratic formula? A) x = b ± b2 - 4ac a B) x = b ± b2 - 4ac 2a C) x = - b ± b2 - 4ac a D) x = - b ± b2 - 4ac 2a

Answer 1

That's pretty ill-formatted but the answer is D

$ax^2 + bx + c = 0$

has roots given by

$x = \dfrac{-b \pm \sqrt{b^2 - 4ac}}{2a}$

Bonus quadratic formulas:

The Shakespeare Quadratic Formulas ($2b$ or $-2b$) are:

$x^2 - 2bx + c \textrm{ has zeros at }x=b \pm \sqrt{b^2-c}$

$ax^2 - 2bx + c \textrm{ has zeros at }x=\frac 1 a( b \pm \sqrt{b^2-ac})$