Basic math problem with Integrating Factors: Differential Equations I was watching a youtube tutorial on Integrating Factors and I'm lost in a part where the derivative of: xy' + 1y becomes xy.
Please I need some clarification on that part.
Secondly.
I was watching a another youtube tutorial on Integrating Factors and I also got lost in this part.
https://i.stack.imgur.com/pmcP6.png
I don't understand how the first line converts to the other, Please I also need some clarification here.
Thanks.

For your first question you just apply the product rule:
$\frac{d}{dx}(xy)=x\frac{dy}{dx}+y=xy'+x$
