(1), because: parabola y=ax? +bx+c and parabola y=( 1/4)x? Same shape, opposite opening direction.
So: a=- 1/4,
Because when x=2, the function has a maximum value.
So: the symmetry axis of the function x=-b/2a=2, that is, -b/[2 *( 1/4)]= 2,
So: b= 1
Substitute the coordinates (2,4), a =- 1/4 and b = 1 into the parabolic analytical formula: 4=(- 1/4)*2? + 1*2+c
Solution: c=3.
So: the analytical formula of parabola is y=-( 1/4)x? +x+3
(2) Because this parabola opens downwards, the axis of symmetry is x=2.
So: when x>0, y decreases with the increase of x.