I thought I could get there via an inequality route. =S
Discriminant=
This implies that the quadratic only has 1 root and this root is repeated. Therefore a graph of this quadratic would have a minimum point that touches the x axis. Hence the entire quadratic would be greater than 0.
For a proof though, would it be better to construct the quadratic first, work all this out and eventually arrive at it must be greater than 0?