Atree of height y meters has approximately b branches, where b = y − 2. each branch has approximately n leaves where n = 9b2 − b. find the approximate number of leaves of a tree as a function of height.
approximate number of leaves of a tree

We are given an expression representing the number of branches in terms of the height of the tree, y: B = y − 2 and the number of leaves n = 9B2 − B. the function of the number of leaves as a function of height is 

n = 9B^2 − B
n = 9(y-2) ^2 − (y-2)
n = 9* (y2-4y+4) -y +4
n = 9y2-36y+36 -y +4
n = 9y2-37y+40