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# How to differentiate this? Watch

1. f(t) = K(t) - K(t-T)

I want to find

i'm unsure of the notation, does the 3rd term represent K as a function of t-T ? I know the 2nd term is showing K is a function of time otherwise it would be written simply Kt, but unsure of the 3rd term. I'm confused
2. Oh btw I believe the answer to be

because K can't be a function of t then t-T in the same equation, so it must mean f(t) = K(t) - tK(t) + TK(t)
3. It does indeed mean K is a function of T-t, where I am assuming T is a constant?
You could differentiate it by using the substitution u=T-t and then the chain rule, should work through fairly easily.

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Updated: December 1, 2010
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