Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[frostshotgg]

Yeah, permutations and combinations are way before precalc, at least when I did it.

[Amperzand]

Given the preceding materiel, they feel as if they should be, but they're in the textbook.

[3man75]

I'm doing a function as it relates to economical question. But I just don't get how to go about this.

Spoiler (click to show/hide)

"The Quantity of x sold of certain product and price p (in dollars) and are related by the equation x = -4p + 400; 0 less than or equal to p less than or equal to 100. A) Express the revenue as a function of x. B) what quantity x maximized the revenue? C) what is the price per unit that must be charged to attain this maximum revenue?

Above is the question. I understand so far that the maximum revenue function so..

R(X) = -4p + 400; Here's how it's modeled thus far in my brain where R is revenue and that X is products. I think this satisfies part A) yes?

For part B) How do I efficiently find the maximum? I got a hint from looking at a friends H.W that it was a parabola where the two rays go down instead of up. I'd draw it but I have not tool for that.

C) Can't be solved without B) so i'm stuck.

Any ideas?

[MagmaMcFry]

Hints:

A) The revenue R is obviously equal to x*p, and you can write p in terms of x by solving the given equation (x = -4p+400) for p.

B) Places where the derivative of a function is zero and its second derivative is negative are always locations where the function is maximized.

[chaotic skies]

So I know this is incredibly simple, but it's confused me to all hell.

Spoiler: Question (click to show/hide)

A circular pon will be placed on a square piece of land. The length of a side of the square is 2x. The radius of the pond is x. The part of the square not covered by the pond will be planted with flowers. What is the area of the region that will be planted with flowers?

(π is supposed to be pi)

So far I've tried 2x²-πx² and 2x²-2πx, but both get a negative answer, which is a problem when your answer is supposed to be the area. Please Help.

[Helgoland]

Whaddya mean supposed to be? That's just pi, plain and simple.

You need to calculate (2x)² - πx², not 2x² - πx². Just blindly applying formulae is a surefire way to get lost in wrong results without having an idea where the problem is: You need to know at every step what you're doing, why it's permissible, why it works, and why you're doing it. (Most of the time this is less complicated than it sounds.)

[chaotic skies]

Oh. Well. Now I know why my head hurts. I always forget the exponents thing >.>

[TheBiggerFish]

When in doubt, put parentheses around it.

[Skyrunner]

In prob&stats, we recently went over something called a "moment-generating function." The problem is, I have no idea why they exist.. what's the point of turning a probability function into a fancy infinite sum with e^t or infinite integral just to get the probability density function? @.@

[Skyrunner]

The problem is I now have to derive a moment-generating function q.q

[Vector]

-snip-

[Amperzand]

So, a sequence of fractions, stated to be arithmetic.

a1: 1/1+sqrt(b)

a2: 1/1-b

a3: 1/1-sqrt(b)

abfoiazbfaifbasiuHALP

[RedWarrior0]

Assuming that 1+sqrt(b) and 1-b and 1-sqrt(b) are the denominators: convert to common denominator. Remember that (x-y)(x+y) = x^2 - y^2.

[Amperzand]

Having messed with it for a while, and coincidentally sought out help from somebody more expert than I,  I believe I understand what I'm doing here.

[hops]

Can anyone tell me what "occur to an even power" mean? All Google shows me are incomprehensible pure mathematics textbooks.