College maths question (basic enough!)

NewApproach

A certain company produces digital cameras. The price-demand function for the cam-
eras is
p(x) = 95.4 - 6x
where p(x) is the wholesale price per camera at which x million cameras can be sold.
Suppose that the cost function is c(x) = 150 + 15.1x. Find the profit function, and determine the number of cameras that should be sold for maximum profit.




Am I right in thinking the profit function is p(x)(x)-c(x)?

Thanks

Fremen

Yes, profit is sale price minus production cost. That's not really mathematics though.

NewApproach

Yes but do you have to multiply the sale price by x to get the total revenue?

NewApproach

I got the previous one...

Another one now though;

9000=3000(1+ r/4)^120

Got down as far as ln(1+ r/4)=0.009155 (correct?)

Now what?!

Thanks!

DancingDaisy

Are you trying to solve for r?

NewApproach

DancingDaisy wrote: »

Are you trying to solve for r?

Yes sorry I should have said that:o

Have a made a balls of it?

Orig Q is: If €3000 is to grow to €9000 over a 10-year period, at what annual rate of interest must it be invested, if compounding is quarterly?

Edit: OOPS just realised I made a stupid silly mistake, should be 40 compounding periods not 120 yes?

Still, I dont get what to do after!!!

LeixlipRed

If you're trying to solve for r you need to use the fact that the exponential and natural log functions are inverses of each other and get the exponential of both sides.