Pgh234 From United States of America, joined Jul 2001, 796 posts, RR: 1
Reply 3, posted (13 years 2 months 1 week 6 days 6 hours ago) and read 3637 times:
OMG, that is SOOOOOO creepy. I am doing the EXACT SAME PROBLEM for my AP Calculus homework as I am reading your post. Do you happen to have the same book as me also? It is a red Calculus book with "Larson-Hostetler-Edwards" Second edition on the bottom of the cover and the problem you are refering to is on Page 178, problem #3a in section 2.7?
anyways, to solve:
xy = 4 dx/dt=10 and find dy/dt when X=8
(x dy/dt + y dx/dt) = 0 (Multiplication Rule as stated above)
dy/dt = -(y/x)dx/dt
dy/dt = - ((1/2)/8) * 10 (Found Y value by solving equation for X=8)
dy/dt = -5/8
Good Luck in Calculus, cuz so far, it sucks!