Given that a,b$\xi$ c are in AP,which of the following is true?

Question

$(a)\;(a-c)^2=4b^2-ac\qquad(b)\;(a-b)^2=4c^2-ab\qquad(c)\;(a-c)^2=4(b^2-ac)\qquad(d)\;(b-c)^2=4(a^2-bc)$