Answer:
1. Vertex on the y-axis (correct, since the x-coordinate of the vertex is 0)
2. Concave down (correct, since the coefficient of the x^2 term is negative)
3. One positive x-intercept (correct, since the discriminant is positive, indicating one real x-intercept)
4. Negative y-intercept (incorrect, since the y-intercept is positive)
5. Line of symmetry at y=3 (incorrect, since the line of symmetry is x=3)
Therefore, the correct answers are 1, 2, and 3.
Explanation: