Answer:
x = 0.75.
Explanation:
y = 4x^2 - 6x + 3.
( I have assumed that the first term is 4x^2 not 4x).
Convert to vertex form:
y = 4(x^2 - 1.5x) + 3
y = 4[ (x - 0.75)^2 - 0.5625 ] + 3
y = 4(x - 0.75)^2 - 2.25 + 3
y = 4(x - 0.75)^2 + 0.75.
So the axis of symmetry is x = 0.75.