Quadratic formula

The quadratic formula is a formula used to solve quadratic equations.

When $$ax^2+bx+c=0$$, x can be found this way: $$x={-b\pm\sqrt{b^2-4ac}\over{2a}}$$.

Example
If a = 5, b = 26 and c = 5, to solve this: $$5x^2+26x+5=0$$, the quadratic formula can be applied.

$$x=\frac{-26+\sqrt{26^2-4(5)(5)}}{2(5)}=\frac{-2}{10}=-0.2$$.

When checked, it should get: 5(0.04) - 5.2 + 5=0.2 - 5.2 + 5=-5 + 5=0. The equation is correct. The square of a negative number is positive: -0.22 = 0.04

The calculation for the golden ratio also uses the formula.