Critical points, several variables

In summary, the critical points of x3 + y3 + 3x2 + 6y2 - 9x + 9y +1 are (-3, -3), (-3, 1), (1, -3), and (1, 1).
  • #1
simba_
19
0

Homework Statement


Find the critical points of

x3 + y3 + 3x2 + 6y2 - 9x + 9y +1

you do not need to define the critical points

Homework Equations





The Attempt at a Solution



i have
df/dx = 3x2 + 6x - 9 and when i solve this x = -3, 1
but i don't know what the corresponding y values are

df dy = 3y2 + 12y + 9 and so y = -3, -1
and here i don't know what the corresponding x values are
 
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  • #2
simba_ said:

Homework Statement


Find the critical points of

x3 + y3 + 3x2 + 6y2 - 9x + 9y +1

you do not need to define the critical points

Homework Equations





The Attempt at a Solution



i have
df/dx = 3x2 + 6x - 9 and when i solve this x = -3, 1
but i don't know what the corresponding y values are

df dy = 3y2 + 12y + 9 and so y = -3, -1
and here i don't know what the corresponding x values are
fx = 0 when x = -3 or x = 1
fy = 0 when y = -3 or y = 1

So both partials are zero at (-3, -3), (-3, 1), (1, -3), and (1, 1).
 
  • #3
tyty
 

Related to Critical points, several variables

What are critical points?

Critical points are points on a graph or function where the derivative or gradient is equal to zero. They are also known as stationary points.

How do you find the critical points of a function?

To find the critical points of a function, you need to take the derivative of the function and set it equal to zero. Then, solve for the variable to find the critical points.

Why are critical points important?

Critical points are important because they can tell us about the behavior of a function. They can indicate the maximum, minimum, or inflection points of a function.

What is the difference between a local and global critical point?

A local critical point is a point on a function where the derivative is equal to zero and it is either a maximum or a minimum within a specific interval. A global critical point is a point on a function where the derivative is equal to zero and it is the maximum or minimum value for the entire function.

Can a function have more than one critical point?

Yes, a function can have multiple critical points. These points can be local or global and they can occur at different locations on the function's graph.

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