We have a parabola that turns upward....the min is found to be the y coordinate of the vertex
In the form y= ax^2 + bx + c , the x coordinate of the vertex = -b/ (2a) = -8 /( 2 * 3) = -8/ 6= -4/3
The minimum is
3 ( -4/3)^2 + 8(-4/3) + 9 =
3 ( 16/9) - 32/3 +9 =
16/3 - 32/3 + 27/3 =
11 / 3