How would you represent a d-ary heap in an array?

Answer this question by:

Giving an expression for J-th-Child(i,j): the index of the j-th child as a function of the index i of the given node, and the child index j within the given node.

Giving an expression for D-Ary-Parent(i): the index of the parent of a node as a function of its index i within the array.

Checking that your solution works by showing that D-Ary-Parent(J-th-Child(i,j)) = i (when you start at node i, and apply your formula to go to a child, and then your other formula to go back to the parent, you must end up back at i).