Why MRS = MUx/MUy (Equation for Marginal Rate of Substitution)

Hi everyone in this video I explain the equation of our MRS, which is our marginal rate of substitution, between two goods, x and Y, which we find by taking the marginal utility associated with good X and divide it by the marginal utility of good y.
0:00 Introduction
0:57 Strategy (Find the slope of the indifference curve to find formula for MRS)
1:46 Rise / Run on the Indifference Curve
2:10 Utility along the indifference curve is constant - the start of the derivation
4:24 Solving for the Slope
The one thing I didn't do in this video is describe why mRS = -'ve of the slope of indifference curve. I didn't want to make too long of a video! I'll do another video on this topic and link to it here when it's done :)
Thank you so much for watching I hope that the video helped!!