# Thread: [SOLVED] Price demand exquation

1. ## [SOLVED] Price demand exquation

I am having problems with the following problem that relates p(price) and demand (x) with the equation:

$
x^2+2xp+25p^2=74,500
$

1. If the price is increasing at a rate of $2 per mo. when the price is$ 30; how do I find the rate of change of the demand?

I understand that I need to implicitly dif. $(2x*x'+2xp'+2px'+50pp')$ but I'm not sure what to plug in after this step...

2. How do I find the rate of change of the price when demand is decreasing 6 units per mo when demand is 150?

Any help would be greatly appreciated

2. You plug in the following:

p' = $2 p =$30

2. You implicitly differentiate, and then plug in:
x' = 6
and equate the equation to: 150

I am not certain of my answers.

3. so for 1) I would end up with

$
2x*x'+2x(2)+2(30)+50(3)(2)=0
$

$
2x*x'+4x+360=0
$

what do I do with the x'?

4. you can plug in the first equation for p=$30 then you find x. with this you can solve the last equation you have found above. 5. I'm confused, can you demonstrate what you mean? 6. Originally Posted by snappyslow22 I am having problems with the following problem that relates p(price) and demand (x) with the equation: $ x^2+2xp+25p^2=74,500 $ 1. If the price is increasing at a rate of$ 2 per mo. when the price is $30; how do I find the rate of change of the demand? I understand that I need to implicitly dif. $(2x*x'+2xp'+2px'+50pp')$ but I'm not sure what to plug in after this step... 2. How do I find the rate of change of the price when demand is decreasing 6 units per mo when demand is 150? Any help would be greatly appreciated first find x when p=30 $x^2+60x+25(30)^2 = 74500$ $x^2+60x+25(900)-74500 =0$ $x^2+60x+100(225-745)=0$ $x^2+60x+100(-520)=0$ $x=\frac{-60\mp\sqrt{3600-(4(-52000))}}{2}$ $x=\frac{-60\mp 10\sqrt{36+4(520)}}{2}$ $x=\frac{-60\mp 10(2)\sqrt{529}}{2}$ $x=\frac{-60\mp 20(23)}{2}$ $x=\frac{20(-3+23)}{2}... or.....x=\frac{20(-3-23)}{2}$ you find the value of x when p=30 now sub it in the formula that you mention before you have the value of x and p and p' you can find x' 7. x^2+2xp+25p^2=74,500 for p=30 you can find x from the equation when the price is increasing at a rate of$ 2 per mo.

last equation you found 2x*x'+4x+360=0 now you have x and you can find the rate of change of the demand namely x'
I hope I could make it clear.