A Level Maths Notes: FP1 – Transforming Differential Equations
Not all differential equations take a standard form which can be solved used a standard result. Most differential equations can only be solved numerically on a computer, to a certain precision, which is always a compromise with the time and computing power available and the required precision. Finding the transformation to use is a matter of experience and intuition and recognition. If you are given the transformation then it is much simpler.
The equation
(1)
may be transformed into a simpler form using the transformation y=vx
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On substituting these expressions into (1) the equation becomes
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The final step is to divide
by
because
it is a common factor, but we can only do this if we include the
condition that
else
we would be dividing by zero. We obtain
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This is a nonhomogenous linear equation which can easily be solved using standard techniques. The solution, once found is transformed back into the original variables x and y.
The equation
(2)
may be transformed using the transformation![]()
The
equation (2) becomes
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This can be directly integrated and transformed back into the original variables x and y to solve the original equation.