$\begin{array}{1 1}(a)\;\large\frac{dN}{dt}=Nr[\large\frac{N}{K}-1] \\ (b)\;\large\frac{dN}{dt}=rN[1-\large\frac{N}{K}] \\(c)\;\large\frac{dN}{dt}=rN[1-\large\frac{K}{N}] \\(d)\;\large\frac{dN}{dt}=rN[1+\large\frac{K}{N}]\end{array}$
