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# Simple Differential Equation Problem watch

1. Once again my simple maths is failing me! I have an example for a 1st order ODE, and it is showing me how to use the integrating factor method. I says I first need to re-express the equation from

x(dy/dx)+y=x to d/dx(xy)=x

I am failing to see how this has happened an really need to if I am able to do my homework! Any helps?
2. If you know how to do integrating factors, simplify the equation, find the IF, and multiply by it.
If not, just notice that xy'+y=(xy)' where ' means 'differentiated wrt x'.
3. product rule

d/dx(xy) = d/dx(x)·y + x·d/dx(y) = y + x(dy/dx)
4. (Original post by dichr0ic)
product rule

d/dx(xy) = d/dx(x)·y + x·d/dx(y) = y + x(dy/dx)
Ah that might be it!
5. (Original post by doggyfizzel)
Ah that might be it!
is it one of the examples in old spec FP1 textbook? i remember being confused about this too, then i realised it was the product rule

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Updated: January 27, 2010
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