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    IB Math AAHL
    /
    Differential Equations
    /

    Skills

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    Differential Equations

    Skill Checklist

    Track your progress across all skills in your objective. Mark your confidence level and identify areas to focus on.

    6 Skills Available

    Track your progress:

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    📖 = included in formula booklet • 🚫 = not in formula booklet

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    📖 = included in formula booklet • 🚫 = not in formula booklet

    Solving Differential Equations

    5 skills
    Separable Variables
    AHL 5.18

    When you have a differential equation in the form

    dxdy​=f(x)g(y)🚫

    you can bring all the y's to one side and all the x's to the other:

    g(y)1​dy=f(x)dx🚫
    ∫g(y)1​dy=∫f(x)dx🚫


    Watch video explanation →
    Particular Solutions
    AHL 5.18

    The solutions to differential equations will usually contain a constant of integration +C. These are called general solutions.


    Often, we are given an initial condition, ie the value of y for a specific x, which we can use to solve for C. The result is the particular solution.

    Watch video explanation →
    Direct Integration
    AHL 5.18

    The easiest differential equations to solve are the ones in the form

    dxdy​=f(x)

    as we can simply integrate:

    y=∫f(x)dx🚫
    Watch video explanation →
    Integrating Factor
    AHL 5.18

    For a differential equation in the form

    dxdy​+P(x)y=Q(x)

    Multiply both sides by integrating factor (often called μ):

    e∫P(x)dx📖

    and notice the product rule on the LHS.

    Watch video explanation →
    Homogeneous Equation
    AHL 5.18
    dxdy​=f(xy​)🚫


    Let y=vx, then v=xy​.


    Note: On IB exams you will be told to use the substitution y=vx.

    Watch video explanation →

    Euler's Method

    1 skill
    Performing Euler's Method
    AHL 5.18

    Mathematically Euler's Method works as follows:

    1. Start at a known point (x0​,y0​)

    2. Pick a step size h such that x0​+nh=xfinal​ for some integer n.

    Repeat the following steps for each n until the desired x-value is reached:

    1. Find the slope dxdy​=f(xn​,yn​)

    2. Find the next x value xn+1​=xn​+h📖.

    3. Find the next y-value yn+1​=yn​+h×f(xn​,yn​)📖

    Watch video explanation →