how to insert a new node on AVL tree using double rotation?

[Vuhelper]

When we insert a new node into an AVL tree, there are four possible cases:
Case I: If new node is inserted in the left subtree of the left child of a, perform single right rotation.
Case II: If new node is inserted in the right subtree of the left child of a. perform left-right double rotation.
Case III: If new node is inserted in the left subtree of the right child of a. perform right-left double rotation.
Case IV: If new node is inserted in the right subtree of the right child of a, perform single left rotation