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#1 2008-05-04 12:50:27

djbip
Member
Registered: 2008-03-27
Posts: 13

derivatives

1.  Given  y= (-1)/(2x-1)²
     Determine the coordinates of the point on the graph where the slope of the tangent is 1/2.

2. Find the equations of the tangent and normal to the curve y= (x ³ - 2x + 4)²\³ (to the power of 2/3) at x=2
      (hint: i'm supposed to use the chain rule for derivatives)

Please help me!!
Thanks!!

Last edited by djbip (2008-05-04 12:52:04)

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#2 2008-05-04 14:06:48

simron
Real Member
Registered: 2006-10-07
Posts: 237

Re: derivatives

1. Here's a hint: take the derivative, then set that equal to 1/2. Now just solve for x and then plug in x for y.


Linux FTW

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#3 2008-05-04 14:31:36

SvenBee
Member
Registered: 2008-03-08
Posts: 106

Re: derivatives

^ good "hint" O.o


e...the red-headed stepchild of math.

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#4 2008-05-04 14:49:09

djbip
Member
Registered: 2008-03-27
Posts: 13

Re: derivatives

simron wrote:

1. Here's a hint: take the derivative, then set that equal to 1/2. Now just solve for x and then plug in x for y.

k...i got it! thanks!
but what about the other one?!
and i need more than a hint on this one!:o

Last edited by djbip (2008-05-04 14:58:26)

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#5 2008-05-04 20:38:30

Daniel123
Member
Registered: 2007-05-23
Posts: 663

Re: derivatives

Substitute x = 2 into the equation of the curve to obtain its correpsonding y coordinate. Then differentiate, and sub x = 2 into dy/dx to find the gradient of the tangent at that point. Then use

to find the gradient of the normal to the tangent at that point. Then use
twice to find the equations of both lines.

Last edited by Daniel123 (2008-05-04 20:38:52)

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