What you are seeing
Concept
1. a controls the 'opening': a>0 → U shape (opens upward), a<0 → ∩ shape (opens downward).
2. b and c move the graph left/right/up/down.
3. Discriminant D = b² - 4ac tells us about roots:
• D > 0 → two different real roots.
• D = 0 → one repeated real root (touches x-axis once).
• D < 0 → no real roots (curve does not cross x-axis).
4. The red dots are where y = 0, i.e., the solutions of ax² + bx + c = 0.