Based on the polarity I think the set up in the video is correct - remember passive sign convention. We can the difference at the nodes has a dependent source in between them, which means they form a supernode with their difference just being the source. In this case Vx is on the positive end and the source = 2 Vx, so the node between the 20 ohm resistor and dependent source must be equal to Vx - 2Vx = -Vx
This dude is a fucking genius
19:55 Isn't it that voltage between 20 oms and 2Vx voltage source is 3Vx?
Based on the polarity I think the set up in the video is correct - remember passive sign convention. We can the difference at the nodes has a dependent source in between them, which means they form a supernode with their difference just being the source. In this case Vx is on the positive end and the source = 2 Vx, so the node between the 20 ohm resistor and dependent source must be equal to Vx - 2Vx = -Vx