Demand function q = 800 - 2p^2 and finding elasticity

[Mathamateur]

For the demand function q = 800 - 2p^2, find the elasticity when p = $12 and q is the number of items produced.

The definition my book gives for elasticity is "E = -p/q x dp/dq "

How would I go about solving this? So far I have:

dp/dq = -4p

Is this correct so far? If so, how would I solve it from here? If not, where have I gone wrong?

Thanks in advance for the help

 

[stapel]

Since the "elasticity" formula requires that you find dp/dq, yes, finding this seems a good start. But you found dq/dp, not dp/dq. What do you need to do to obtain "dp/dq"?

Once you have that, plug in the rest of the given formula, and simplify.

Eliz.

 

[Mathamateur]

Here is what I came up with. Could someone tell me whether this is right or wrong and if wrong show me how to solve the problem.

E = -4p ( p/800-2p)

p = 12

E = -4 X 12 (12/800-288)

* E = -1.125 *