Variable Separable

http://www.cse.salford.ac.uk/physics/gsmcdonald/M2_02_Separation_of_Variables.pdf

Initial Value Problems

https://www.saylor.org/site/wp-content/uploads/2012/09/MA102-5.5.4-Equations-and-Initial-Value-Problems.pdf

First Order Linear Differential Equations

https://www3.nd.edu/~apilking/Calculus2Resources/Lecture%2019/Section_%2092_Linear_EquationsSolutions%20copy.pdf

Homogeneous Differential Equations

https://www.tau.ac.il/~levant/ode/lesson_4.pdf

http://blogs.rrc.ca/wiseguys/wp-content/uploads/2013/12/Solutions-of-Solving-First-Order-Homogeneous-Differential-Equation-2.pdf

Growth and Decay

http://www.swl.k12.oh.us/Downloads/5-6%20Growth%20and%20Decay.pdf

Newton's Law of Cooling

http://ksuweb.kennesaw.edu/~sellerme/sfehtml/classes/math2202/newtonslawofcoolingsolutions.pdf

Mixing

https://math.dartmouth.edu/archive/m8s00/public_html/hw3sup/mixing.pdf