1. A simple example 2. How to solve with some code in R (4:10) 3. The importance of using a small step size (07:40) 4. How to solve two differential equations (08:05) y0=70 k=0.2 dt=1 t=seq(0,40,dt) Y=NULL Y[1]=y0 for (i in 1:(length(t)-1)){ Y[i+1]=Y[i]-k*Y[i]*dt } plot(t,Y,type="l",col="blue") # Analytic solution yy=y0*exp(-k*t) lines(t,yy,col="red")