/sci/ - Science & Math

>>11054214
It is a babby differential equation my textbook. I started to solve it as-is and then when the algebra became too ridiculous I looked online and found that everyone used substitution to do it instead. This is basically the last step where you plug your substituted a and b, also a' a'' b' and b''.....so it was in the step of differentiating a and b is where I was wondering, since A and B would be considered a constant.

When would it change?