A tree of height y meters has approximately B branches, where B = y − 2. Each branch has approximately n leaves where n = 9B^2 − B. Find the approximate number of leaves of a tree as a function of height.

Approximate number of leaves of a tree.
I tried 9y^2-37y+38 but it's wrong.

Question

A tree of height y meters has approximately B branches, where B = y − 2. Each branch has approximately n leaves where n = 9B^2 − B. Find the approximate number of leaves of a tree as a function of height.

Approximate number of leaves of a tree.
I tried 9y^2-37y+38 but it's wrong.

cruffo · Answer

The answer looks to me ok:
$$9(y-2)^2 - (y-2)$$
$$9(y^2-4y+4) - y + 2$$
$$9y^2-36y+36-y+2$$
$$9y^2-37y+38$$

dumbcow · Answer

hmm yeah that looks good to me too... how do you know it wrong?

anonymous · Answer

Some one told me that it is only for one branch so you need to multiply it by B (y-2). I did that and got 9y^2B-18y^2-37yB+74y+38B-76 but I doesn't look right.

anonymous · Answer

I'm doing this on webassign and it tells you if the answer you put in is right or not.

cruffo · Answer

Ah... 
$$(y-2)(9y^2-37y+38)$$

dumbcow · Answer

oh i missed that..."Each branch" 
ok take answer and multiply by (y-2)

cruffo · Answer

same here...tricky :)

anonymous · Answer

Is 9y^2B-18y^2-37yB+74y+38B-76 right?

cruffo · Answer

too many letters!

anonymous · Answer

Haha that's why I don't know if I should put that answer in or not.

cruffo · Answer

$$(y-2)(9y^2-37y+38)$$
$$9y^3-37y^2+38y - 18y^2+74y - 76$$
gather like terms ..

anonymous · Answer

hmm I put in 9y^3-55y^2+112y-76 and it's still says it's wrong.

cruffo · Answer

yah, Idk :(

cruffo · Answer

what you have there looks ok to me

anonymous · Answer

Thank you!