related rates help.
Suppose x thousand watches can be sold at p dollars per watch where p+x^2 = 144. How fast is the demand changing when x=9, p=63 and the price per watch is increasing at the rate of $2/week?

Please do a step by step explanation. The answer is dx/dt = -1/9 so lets see how they got that. thanks.

Question

related rates help. 
Suppose x thousand watches can be sold at p dollars per watch where p+x^2 = 144. How fast is the demand changing when x=9, p=63 and the price per watch is increasing at the rate of $2/week?

Please do a step by step explanation. The answer is dx/dt = -1/9 so lets see how they got that. thanks.

anonymous · Answer

I solved it .. in 10 seconds ;)

anonymous · Answer

$$ p+x^2 = 144 $$ derivate this with respect to t  $$ \frac{dp}{dt} +2x \frac{dx}{dt} = 0 $$

substitute x=9 and dp/dt =2 you will have your answer.

anonymous · Answer

why can't i do this stuff? im so terrible. thanks

anonymous · Answer

Naah you are just fine ..