Answer:
The line of symmetry is x=2
Step-by-step explanation:
Given:
We are given a quadratic equation and to find the line of symmetry.
As we know the line of symmetry of parabola passes through the x value of vertex.
If vertex of parabola is (h,k) then equation of line of symmetry x=h
So, first we find the vertex of parabola.
For equation: 

For given equation, a=-3 and b=12
Therefore, 

Hence, The line of symmetry of given parabola is x=2