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Thursday, April 10, 2014

Finding Equation - Curve, 14

Category: Differential Equations, Integral Calculus, Analytic Geometry, Algebra

"Published in Newark, California, USA"

Find the equation of the curve for which y" = 2, and which has a slope of -2 at its point of inflection (1, 3).

Solution:

The concavity of a curve is equal to the second derivative of a curve with respect to x. In this case, y" = d²y/ dx². Let's consider the given concavity of a curve



We can rewrite the above equation as follows



Multiply both sides of the equation by dx, we have 




Integrate on both sides of the equation, we have 





The point of inflection is a point where the direction of the concavity of a curve will start to change. In this case (1, 3) is the point of inflection of a curve. Since it is also included in the curve, then we can use it to substitute the value of x and y later in the problem.

Substitute the value of the given slope and the point of inflection to the above equation in order to solve for the value of a constant, we have





Hence, the above equation becomes 



Multiply both sides of the equation by dx, we have 




Integrate on both sides of the equation, we have 






In order to solve for the value of a constant, substitute the value of x and y from the coordinates of a given point of inflection to the above equation, we have 






Therefore, the equation of a curve is