find equation of a parabola f(x)=√(4-x^(2))

I'm not sure if I'm reading this question correctly. The equation y = sqrt(4-x^2) is a semicircle, it simplifies to y^2 = 4 - x^2 ---> y^2+x^2=4 (This is the equation of a circle with radius 2, but since we are only taking the positive sqrt, it is the half of the circle in the positive y axis.)

If the equation is y = v4-x^2, then this is already the equation of a parabola. With the general form being y = a(x-h)^2 + k, a = -1, h = 0, k = v4.