iLoveEatingPie (November 30, 1999 at 12:00 am)

Why is the dy/dx necessary at the end when finding the derivative of the multiplied functions? I don't remember writing it when using that rule.

virginialikesyou (November 30, 1999 at 12:00 am)

Differential Equations usually comes after Multivariable Calculus, where partial differentials is fully covered. I believe this set of videos is fine without the partial differentials review. Nice work, as always Khan! <3

tam3ree (November 30, 1999 at 12:00 am)

@MrNoturaveragerednek Differential equations are mostly used in physics in engineering. Basically it's very useful when working with objects in perpetual movement. The car you drive, the satellites that allows GPS to function and much more were designed much more effectively because of differential equations.

MrNoturaveragerednek (November 30, 1999 at 12:00 am)

I never understood algebra, or calculus or Trigonometry or whatever rocket science math this is supposed to be, who the hell uses this stuff in real life anyway?

middleCmusic (November 30, 1999 at 12:00 am)

Thank you Sal!!! :)

9588alamALI (November 30, 1999 at 12:00 am)

SIR i literally have no words to how much you are helping us students ! God bless you ! 

TheWingflyer (November 30, 1999 at 12:00 am)

@RecLuseGurL91 You're not "stupid" for not knowing this stuff. Your educational background's just short in the area. You'd only be "stupid" if you rejected knowledge.

MrPlender (November 30, 1999 at 12:00 am)

@JohnNumberThree Yes, it's multivariate and it doesn't take much to check...the function Psi depends on y AND x. Hence, there's more than one variable = multi. I'm no expert on this either but as far as I can tell he's taking the total derivative: the function depends directly on x and indirectly on x through y.

m2moun1 (November 30, 1999 at 12:00 am)

psy function , we can replaced with another function " to make it easier psy looks scariness " just for that

SalsaTiger83 (November 30, 1999 at 12:00 am)

I had to view this video 5 times before I noticed that y is a function of x -.-