Anybody good with word problems?

Question

k_lynn · Answer

Shoot them at me

anonymous · Answer

attachment

k_lynn · Answer

To be honest I have no Idea on this one... but I think I know someone who can help you. @eric_d  @PaulaLovesSchool13 @igreen can you help her?

anonymous · Answer

thank you

anonymous · Answer

Do you know calculus?

anonymous · Answer

Barely Im in Pre-Calculus right now

anonymous · Answer

Damn, no calc then. I know how to do this with derivatives, but not without, sorry.

anonymous · Answer

No I have to solve this with cal because its part of the practice problems I want to understand how to do this.

anonymous · Answer

Well, you start by making a function for it, like it says. Do you know how to start?

anonymous · Answer

I have no idea where to start

anonymous · Answer

Okay, why don't we say that the length of the rectangle is y and the width is x?

anonymous · Answer

|dw:1410988776005:dw|

anonymous · Answer

So then you get two equations: A= xy and 2x + y = 600

anonymous · Answer

Do you know how to get a quadratic equation from those two equations?

anonymous · Answer

is it like when you do f(g(x))?

anonymous · Answer

It's just a bit of simple rearranging. Take 2x + y = 600 and isolate for y, then plug that value into the second equation.

anonymous · Answer

y=-2x+600
y=x(-2x+600)

like this?

anonymous · Answer

Er, no. More like:

2x + y = 600
y = 600 - 2x                      (2)

Insert (2) into A= xy

A = xy
A = x(600-2x)
A = 600x - 2x^2

anonymous · Answer

You might've just made a typo and written y instead of A.

anonymous · Answer

Because otherwise it's right.

anonymous · Answer

No I messed up before and as I was looking at it I realized where I went wrong

anonymous · Answer

Anyways, so know we have the equation A = 600x - 2x^2. Can you take the derivative of this?

anonymous · Answer

what is derivative?

anonymous · Answer

If you can't, you can always just use a graphing calculator to find the max point.

anonymous · Answer

The max point will be the x-value that gives you the max area.

anonymous · Answer

Then you plug in the x-value into the previous equation to find the max area.

anonymous · Answer

I dont really understand what your talking about.

anonymous · Answer

No wait, I've got, the way you do this without derivatives.

anonymous · Answer

Can you convert the equation into the form y = a(x-h)2 + k

anonymous · Answer

Im lost lol

anonymous · Answer

ohh okay

anonymous · Answer

The k value is the max area.

anonymous · Answer

You should get 45 000

anonymous · Answer

yeah I just got that

anonymous · Answer

Thank you very much