12 is a
13 is b
14 is d
15 is 1 217/1250
Axis of symmetry = -b/2a
y + 3x - 6 = -3(x-2)² + 4
y + 3x - 6 = -3 ( x²-4x+4) + 4
y + 3x - 6 = -3x² + 12x -12 + 4
y + 3x - 6 = -3x² + 12x -8
y = -3x² + 12x - 3x -8 + 6
y = -3x² + 9x -2
(a=-3, b=9, c=-2)
Axis of symmetry = -b/2a = -9/2(-3) = -9 / -6 = -3 / -2 = 3/2
Hence, option A) x=3/2 is the correct answer.
Correct! lines that have undefined slopes are always parallel to the y-axis as the change in x is 0. A gradient is calculated by the change in y divided by the change in x and anything divided by 0 is referred to as undefined.

(calculation for a gradient)
Hope that helps sorry if its a bit confusing :)