Differential equation of all circles radius 5, with their centres on the y-axis.

Question

$(a)\;x^2 (\frac{dx}{dy})^2+x^2+25=0 \\ (b)\;x^2 (\frac{dy}{dx})^2+x^2+25=0 \\ (c)\;x^2 (\frac{dx}{dy})^2-x^2+25=0 \\ (d)\;y^2(\frac{dx}{dy})^2-x^2+25$