Math Is Fun Forum

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)

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.

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SvenBee

Member

Registered: 2008-03-08

Posts: 106

Re: derivatives

^ good "hint" O.o

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djbip

Member

Registered: 2008-03-27

Posts: 13

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.

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)

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)