Christos
Derivatives,
There is this problem that asks me to find the derivative of f(x)=2x^2 ONLY by making use of this formula: f'(x)=lim(h-->0)(f(x+h)-f(x))/h
My Question is this:
http://screencast.com/t/fdJEOQduGCj
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AravindG
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Yep just use that formula
Christos
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Check at my question
AravindG
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f(x+h)=?
f(x)=?
AravindG
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Can you write those?
julian25
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?????? it is right?????? the derivative is 4x
Christos
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f(x)= 2x^2 f(x=h)= 2(x+h)^2
AravindG
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*f(x+h)
AravindG
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f(x+h)= 2x^2 f(x=h)= 2(x+h)^2
Christos
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But my approach (the one with the red letters) gives 0. And I didn't do any mistake
Christos
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thats what I said @AravindG
Christos
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ah yea +**
AravindG
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What is your problem ? You are getting correct answer 4x ?
Christos
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No, look. The black letters is the solution manual. On the other hand the RED letters are my approach. The solution gives 4x. My solution gives 0. Both solutions doesn't have any mathematical mistake. ( and it's driving me crazy)
AravindG
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Why 0 ? You are told x=0 ?
Christos
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lim (h--->0)
AravindG
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that will be 0+4x .I dont see 0 anywhere
AravindG
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0+4x=4x
Christos
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@AravindG
AravindG
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so option 1 will be correct
Christos
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buth both options doesn't have any mathematical mistakes. Agree?
AravindG
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tell me which options you are speaking of
Christos
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the red
AravindG
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I see 4 options
AravindG
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Which do you mean by saying both ?
Christos
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Wait. Let me write the whole thing here on Open Study , 1 sec
AravindG
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k
Christos
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Forget it I got my mistake, jeez and phew
AravindG
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lol Great you figured it out yourself :)