Solving quadratic equations

Lesson 3: The nature of the roots

From previous discussions, we know that an equation of the form y=ax^2+bx+c has two roots, but the roots are not always distinct. Take, for example, the equation

display equation

We can see that x = –2 when y = 0. This occurs twice, so we call it a double root. It is a single distinct result, but still considered as two roots.

What happens when the equation will not factor over the set of real numbers? Consider

 
y=x^2+9
(1)

From equation (1) it is clear that when