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

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Homework Help Overview

The problem involves a function y = g(x) and requires writing a differential equation of the form "dy/dx = f(x,y)" such that g is one of its solutions. The context includes a tangent line to the graph of g that intersects the x-axis at a specific point.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the relationship between the slope of the tangent line and the points it intersects, specifically questioning how to express the slope in terms of the given points.

Discussion Status

Some participants have provided insights into expressing the slope of the tangent line, while others are seeking clarification on the reasoning behind the proposed differential equation. There appears to be ongoing exploration of the problem without a definitive consensus.

Contextual Notes

Participants note the challenge of understanding both the reasoning and the methodology behind deriving the differential equation from the given conditions.

negatifzeo
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Homework Statement


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).



Homework Equations





The Attempt at a Solution


The solution is y'=2y/x. I'm having trouble seeing both why and how.
 
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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).
 
Thank you so much!
 
negatifzeo said:

Homework Statement


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).



Homework Equations





The Attempt at a Solution


The solution is y'=2y/x. I'm having trouble seeing both why and how.

Write the equation of line with m = g'(x), x0=x/2 and y0=0. Then try to recover that ODE.

AB
 

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