That is how I did it when I followed the example in my textbook. The example used the test source method.Okay great! So I got RC of 5, too with an Req of 1.25. I wish my teacher had taught that. It's not her fault. There are just a ton of morons in that class and they slow the class down so much that I think we just moved on. We were probably supposed to read it and I missed that note. Anyway, it is an easy concept once you're aware of it. So anytime there is a dependent source you remove the capacitor/inductor and replace it with a test voltage with a test current and solve that way? Just want to get everything correct in my head.
Then I did it again using node-voltage method.
I got same differential equation both time.