Math  Limits/Derivatives
posted by Jess .
If a pricedemand equation is solved for p, then price is expressed as p = g(x) and x becomes the independent variable. In this case, it can be shown that the elasticity of demand is given by E(x) =  [g(x) / xg'(x)]. Use the given pricedemand equation to find the values of x for which demand is elastic and for which demand is inelastic.
p = g(x) = 12960  0.1x^2
I am really stuck on this question and don't know how to start, could someone please show me?

you have to remember that inelastic means that E(x) > 0
(I think)
E(x) = [(12960.1x^2)/(.2x^2)]
= 64800/x^2  .5
E(x) > 0 means x < 360
That sound familiar? Or am I way off base here?