Mathematics for IGCSE & O level - Graphs Of Functions (Section 1 - No. 6)
For a quadratic function to have only one real root, which of the following is true?
The discriminant is greater than zero.
The vertex lies on the x-axis.
The graph opens downwards.
The y-intercept is zero.
Forklaring
One real root means the graph touches the x-axis at the vertex.