(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.