Question

How do use the discriminant to find all values of b for which the equation `3x^2+bx+5=0` has one real root?

Answer 1

`b=+-2sqrt15`

Explanation:

The discriminant is

`Delta=b^2-4ac=b^2-4*3*5=b^2-60`

The discriminant will be null if the equation has one real root, then it must be:

`b^2-60=0`

that's

`b=+-sqrt60=+-2sqrt15`