ACEpath
Select Subject
Select Unit

Slope Fields

Graphical representation showing dydx\frac{dy}{dx} at various points (x, y).

  • Each small line segment has slope = dy/dx at that point
  • Solution curves follow the slope field pattern

Separation Of Variables

For differential equation of form dydx=g(x)h(y)\frac{dy}{dx} = g(x)h(y):

  1. Separate: dyh(y)=g(x)dx\frac{dy}{h(y)} = g(x)dx
  2. Integrate both sides: 1h(y)dy=g(x)dx\int \frac{1}{h(y)}dy = \int g(x)dx
  3. Solve for y (if possible)

Particular Solutions

General solution contains +C (arbitrary constant). Particular solution: Use initial condition y(x0) = y0 to find C.

Exponential Growth And Decay

For dydt=ky\frac{dy}{dt} = ky: y=y0ekty = y_0 e^{kt}

  • k > 0: Exponential growth
  • k < 0: Exponential decay
  • Half-life: t1/2=ln2kt_{1/2} = \frac{\ln 2}{|k|}

Logistic Differential Equation

dPdt=kP(1PL)\frac{dP}{dt} = kP\left(1 - \frac{P}{L}\right)

where:

  • P = population at time t
  • k = growth rate constant
  • L = carrying capacity (maximum sustainable population)

Carrying Capacity

Maximum population that environment can sustain.

  • Growth rate maximum when P = L/2
  • Population approaches L as t -> ∞