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Help with differentials?

How would you find the general solution of

(1-x^2) y' - xy = 1

I tried by using the reverse of differentiation by parts but I got nowhere.

1 Answer

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  • Niall
    Lv 7
    6 years ago
    Favorite Answer

    This is a linear equation, put it in the form of y' + p(x)y = g(x):

    y' - x / (1 - x^2) * y = 1 / (1 - x^2)

    Now we find the integrating factor, which is I = e^( ∫ P(x))

    I = e^[ ∫ -x / (1 - x^2) * dx]

    I = e^[1/2 * ln(1 - x^2)]

    I = (1 - x^2)^1/2

    Multiply throguh by the integrating factor:

    (1 - x^2)^1/2 * y' - x / (1 - x^2)^1/2 * y = 1 / (1 - x^2)^1/2

    After we multiply through by the integrating factor, the left side becomes the derivative of the product of y and the integrating factor (which you can check with the product rule):

    d/dx [(1 - x^2)^1/2 * y] = 1 / (1 - x^2)^1/2

    Integrate both sides:

    (1 - x^2)^1/2 * y = arcsin(x) + C

    y = [arcsin(x) + C] / (1 - x^2)^1/2

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