Register to reply

Find the x coordinate of the stationary point of the following curves

by studentxlol
Tags: coordinate, curves, point, stationary
Share this thread:
Nov28-11, 04:24 AM
P: 39
1. The problem statement, all variables and given/known data

Find dy/dx and determine the exact x coordinate of the stationary point for:

(a) y=(4x^2+1)^5

(b) y=x^2/lnx

2. Relevant equations

3. The attempt at a solution

(a) y=(4x^2+1)^5



Find x... How?

(b) y=x^2/lnx

dy/dx=2xlnx-x^2 1/x / (lnx)^2

2xlnx-x^2 1/x / (lnx)^2=0

Find x... How?
Phys.Org News Partner Science news on
Experts defend operational earthquake forecasting, counter critiques
EU urged to convert TV frequencies to mobile broadband
Sierra Nevada freshwater runoff could drop 26 percent by 2100
Nov28-11, 04:38 AM
P: 950
Quote Quote by studentxlol View Post

Find x... How?
re 1st prob:

Then either 40x = 0 or (4x^2+1)^4 = 0.

and solve the above two equations.
Nov28-11, 06:58 AM
Sci Advisor
PF Gold
P: 39,568
You are aware that [itex]x^2/x= x[/itex] aren't you?

[itex]y= x^2/ln(x)[/itex]: [itex]y'= (2xln(x)- x)/(ln(x))^2= 0[/itex]
Use parentheses! What you wrote was [itex]y'= 2x ln(x)- (x/(ln(x))^2)= 0[/itex].

Multiply both sides of the equation by [itex](ln(x))^2[/itex]
and you are left with 2x ln(x)- x= x(2ln(x)- 1)= 0. Can you solve that?

Register to reply

Related Discussions
Shell method to find volumes: need to find intersections of the curves involved? Calculus 0
Polar Coordinate Area between two curves Calculus & Beyond Homework 6
Mathematica - Colour each 2D point by a third coordinate for each point? General Math 3
Coordinate curves problem Calculus 3
Stationary point Advanced Physics Homework 1