Which test can be used to determine whether a critical point (a, b) is a local minimum, local maximum, or a saddle point for a function f(x,y)𝑓(𝑥,𝑦)?a.First Partial Derivative Testb.Critical Point Testc.Second Partial Derivative Testd.Lagrange Multiplier Test
Question
Which test can be used to determine whether a critical point (a, b) is a local minimum, local maximum, or a saddle point for a function f(x,y)𝑓(𝑥,𝑦)?a.First Partial Derivative Testb.Critical Point Testc.Second Partial Derivative Testd.Lagrange Multiplier Test
Solution
The Second Partial Derivative Test (option c) can be used to determine whether a critical point (a, b) is a local minimum, local maximum, or a saddle point for a function f(x,y).
Here are the steps to perform the Second Partial Derivative Test:
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Find the first partial derivatives fx and fy and set them equal to zero to solve for the critical points.
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Find the second partial derivatives fxx, fyy, and fxy.
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Evaluate the second partial derivatives at the critical point(s).
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Use the discriminant D = (fxx)(fyy) - (fxy)^2.
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If D > 0 and fxx > 0, then the function has a local minimum at the point. If D > 0 and fxx < 0, then the function has a local maximum at the point. If D < 0, then the function has a saddle point at the point. If D = 0, then the test is inconclusive.
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