Can someone please explain why marks were taken off in this limit question • Physics Forums

FrancisG · 2018-02-15T01:02:55+00:00

My teacher says I have to solve all the limits at once, but I don't understand why it is mathematically incorrect to solve one limit before the other. The test is here:

Thread 'How to Find Critical Points of function f(x,y,z)'

Hi everybody If we have not any answers for critical points after first partial derivatives equal to zero, how can we continue to find local MAX, local MIN and Saddle point?. For example: Suppose we have below equations for first partial derivatives: ∂ƒ/∂x = y + 5 , ∂ƒ/∂y = 2z , ∂ƒ/∂z = y As you can see, for ∇ƒ= 0 , there are not any answers (undefined)

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MHB Can someone please explain why marks were taken off in this limit question

Thread 'How to Find Critical Points of function f(x,y,z)'

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