help needed in m2 question Watch

Tommy07
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#1
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A particle moves in a straight line with velocity v given by v= 3t-4t3 +1 at time ts after passing through a fixed point O in that line. Find its maximum velocity!

i know its probably really easy but i just started m2 and havent got the hang of it yet so please help me with this question. thanx!
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Chewwy
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just find the max of 3t-4t^3 +1 by differentiation. i'm sure you can do that dollface.
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Tommy07
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dollface????

so i just do dy/dx and equal that to 0 to find t then i subsitute it back into the original formula?
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Tommy07
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well i tried that and i dont get the correct answer which is 2m/s i get 1m/s..????
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Chewwy
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v= 3t-4t^3 +1
dv/dt = 3 - 12t^2 = 0
t^2 = 1/4
t = 1/2

v = 3(1/2) - 4(1/2)^3 + 1 = 1.5 - 0.5 + 1 = 2
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Tommy07
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opps!! forgot to add the one!!
thanx chewwy!
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