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Homework Help: Differential Equation (Solution known, but I don't understand)

  1. Jan 14, 2010 #1
    1. The problem statement, all variables and given/known data
    In this problem, a function y= g(x) is described. Write a differential equation of the form "dy/dx=f(x,y) having the function g as it's solution (or one of it's solutions).

    The line tangent to the graph of g at the point (x,y) intersects the x-axis at the point (x/2,0).

    2. Relevant equations

    3. The attempt at a solution
    The solution is y'=2y/x. I'm having trouble seeing both why and how.
  2. jcsd
  3. Jan 14, 2010 #2


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    The tangent passes through a point on the curve, call it (x,y) and has a slope y'. That tangent also passes through (x/2,0). Express y' by finding the slope of the line through the two points (x,y) and (x/2,0).
  4. Jan 14, 2010 #3
    Thank you so much!
  5. Jan 14, 2010 #4
    Write the equation of line with m = g'(x), x0=x/2 and y0=0. Then try to recover that ODE.

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