Find the critical point of the function f(x,y)=−(30x+6y^2+ln(|x+y|))

c=

1 answer

To find the critical point of the function f(x, y) = -(30x + 6y^2 + ln(|x+y|)), we need to take the partial derivatives with respect to x and y and set them equal to zero.

First, let's find the partial derivative with respect to x (f_x):

f_x = -30 - 1/(x+y) (since the derivative of ln(|x+y|) with respect to x is 1/(x+y))

Next, let's find the partial derivative with respect to y (f_y):

f_y = -12y/(x+y) - 1/(x+y) (since the derivative of ln(|x+y|) with respect to y is 1/(x+y))

Setting both partial derivatives equal to zero:

-30 - 1/(x+y) = 0
-12y/(x+y) - 1/(x+y) = 0

To simplify the equations, we can multiply through by (x+y) to get rid of the fraction:

-30(x+y) - 1 = 0
-12y - (x+y) = 0

Now, we can solve these two equations simultaneously.

From the first equation, we have:

-30x - 30y - 1 = 0
-30x - 30 = 30y
x = -1/30 - y

Substituting this into the second equation:

-12y - (x+y) = 0
-12y - (-1/30 - y + y) = 0
-12y + 1/30 = 0
-12y = -1/30
y = 1/360

Now, substituting the value of y back into x = -1/30 - y:

x = -1/30 - 1/360
x = -12/360 - 1/360
x = -13/360

Therefore, the critical point of the function f(x, y) = -(30x + 6y^2 + ln(|x+y|)) is c = (-13/360, 1/360).