Finding Local Max/Min with f(x)= x + 9/x: Explained

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In summary, a quick local max/min question is a type of calculus problem where you find the maximum or minimum value of a function within a specific interval by finding its critical points. To find these points, you take the derivative and set it equal to zero. Local max/min refers to the highest or lowest point within an interval, while global max/min refers to the highest or lowest point over the entire function. You can determine if a critical point is a local max/min by using the first or second derivative test. These types of problems have various real-world applications in fields like economics and physics.
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wr1015
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ok so in the problem f(x)= x + 9/x, I know how to write where f is increasing, but how do you write how it's decreasing? Is it written as [-3,0)U(0,3]? since x=0 is a vertical asymptote wouldn't all the x-values between -3 and 3 be as close to 0 as possible?
 
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wouldnt f(-3) = -3 + 9 / (-3) = -3 -3 = -6
 
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mathmike said:
wouldnt f(-3) = -3 + 9 / (-3) = -3 -3 = -6

yeah that's my local min at (-3,-6).
 

1. What is a quick local max/min question?

A quick local max/min question is a type of problem in calculus where you are asked to find the maximum or minimum value of a function within a specific interval. This can be done by finding the critical points of the function and evaluating them within the given interval.

2. How do I 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. Solve for the variable to find the critical points. These points represent where the slope of the function is equal to zero, which can indicate a potential maximum or minimum value.

3. What is the difference between a local max/min and a global max/min?

A local max/min is the highest or lowest point within a specific interval, while a global max/min is the highest or lowest point over the entire domain of the function. A function can have multiple local max/min points, but only one global max/min point.

4. How do I determine if a critical point is a local max/min?

You can determine if a critical point is a local max/min by using the first or second derivative test. The first derivative test involves evaluating the sign of the first derivative on either side of the critical point. If the sign changes from positive to negative, then the critical point is a local maximum, and if the sign changes from negative to positive, then the critical point is a local minimum. The second derivative test involves evaluating the sign of the second derivative at the critical point. If the second derivative is positive, then the critical point is a local minimum, and if it is negative, then the critical point is a local maximum.

5. Are there any real-world applications of local max/min problems?

Yes, local max/min problems have many real-world applications, especially in fields such as economics and physics. For example, in economics, local max/min problems can be used to determine the optimal production level for a company to maximize profits. In physics, they can be used to find the path of a projectile to reach the highest point or the shortest path between two points.

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