Curve with stationary points

  • Thread starter pip_beard
  • Start date
  • #1
14
0

Homework Statement


A curve is defined for x<-2 by the equation y=((x^2)+3)sqr(x+2)

a) Show that dy/dx=0 when x=-1 and find the x-coordinate of the other stationary point.

b) Find the value of d^2y/dx^2 when x=-1 hence determine whether the turning point is max or min.


Homework Equations





The Attempt at a Solution


y=((x^2)+3).(x+2)^1/2

Differentiate by product rule : u=x^2 +3 v=(x+2)^1/2
u'=2x v'=1/2((x+2)^1/2)

dy/dx= (x^2+3).0.5(x+2)^(-0.5) + (x+2)^0.5 . 2x

Where do i go from here>??
 

Answers and Replies

  • #2
14
0
Then sub in -1 and i get dy/dx=0.. but how do i find the second stat point?>?
 
  • #3
Mentallic
Homework Helper
3,798
94
You need to solve dy/dx=0 like you would any other equation.
Substituting in x=-1 doesn't help you since you already know it's a stationary point so of course you'll get an answer of dy/dx=0 for x=-1.
 

Related Threads on Curve with stationary points

  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
9
Views
1K
  • Last Post
Replies
16
Views
2K
  • Last Post
Replies
6
Views
1K
  • Last Post
Replies
3
Views
2K
Replies
9
Views
3K
  • Last Post
Replies
9
Views
5K
  • Last Post
Replies
12
Views
2K
Top