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For \(f(x, y, z)=x^{2}-y^{2}+z^{2},\) find \(f(-1,2,3)\) and \(f(2,-1,3)\)

Short Answer

Expert verified
For \( f(-1, 2, 3) = 6 \) and for \( f(2, -1, 3) = 12 \).

Step by step solution

01

- Understand the function

First, it's important to understand the given function: \[ f(x, y, z) = x^2 - y^2 + z^2 \]
02

- Substitute values for the first set of points

Substitute \(x = -1\), \(y = 2\), and \(z = 3\) into the function. The function becomes: \[ f(-1, 2, 3) = (-1)^2 - 2^2 + 3^2 \]
03

- Calculate the first set of points

Calculate the value: \[ (-1)^2 = 1, \]\[ 2^2 = 4, \]\[ 3^2 = 9. \]Then, \[ 1 - 4 + 9 = 6. \]
04

- Final value for the first set

Thus, \( f(-1, 2, 3) = 6 \).
05

- Substitute values for the second set of points

Substitute \(x = 2\), \(y = -1\), and \(z = 3\) into the function. The function becomes: \[ f(2, -1, 3) = 2^2 - (-1)^2 + 3^2 \]
06

- Calculate the second set of points

Calculate the value: \[ 2^2 = 4, \]\[ (-1)^2 = 1, \]\[ 3^2 = 9. \]Then, \[ 4 - 1 + 9 = 12. \]
07

- Final value for the second set

Thus, \( f(2, -1, 3) = 12 \).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Function Evaluation
Evaluating a function means you plug in specific values for the variables in the function and calculate the result. For example, in our original function \[ f(x, y, z) = x^2 - y^2 + z^2 \], we evaluated the function by substituting the values of -1, 2, and 3 for x, y, and z respectively. To do this, replace the variables in the function with the given numbers. Next, follow the arithmetic operations to solve the function step-by-step. This process is especially useful in multivariable calculus, as it allows you to find specific function values at given points.
Partial Derivatives
Partial derivatives are used to find the rate at which a function changes with respect to one of its variables, holding the others constant. Though this exercise didn't explicitly involve partial derivatives, understanding them is crucial for deeper understanding. To find a partial derivative, differentiate the function with respect to one variable while treating the other variables as constants. For our function \[ f(x, y, z) = x^2 - y^2 + z^2 \], the partial derivative with respect to x is \[ \frac{\text{\text{∂}}f}{\text{\text{∂}}x} = 2x \]. Similarly, the partial derivatives with respect to y and z can be found by differentiating with respect to these variables.
Coordinate Substitution
Coordinate substitution involves plugging specific values for the variables into a function to evaluate it at a particular point. In our given function \[ f(x, y, z) = x^2 - y^2 + z^2 \], you performed coordinate substitution twice: once with the coordinates (-1, 2, 3) and another time with (2, -1, 3). The substitution steps make it simple to understand how changing the input values affects the output of the function. This technique is straightforward but powerful in multivariable calculus as it helps to visualize how functions behave over their domains.
Algebraic Manipulation
Algebraic manipulation is about rearranging and simplifying expressions to make them easier to work with. When you substituted (-1, 2, 3) into the function \[ f(x, y, z) = x^2 - y^2 + z^2 \], the function became \[ f(-1, 2, 3) = (-1)^2 - 2^2 + 3^2 \]. You simplified this step-by-step: \[ (-1)^2 = 1, \ 2^2 = 4, \ 3^2 = 9, \ 1 - 4 + 9 = 6 \]. This method involves basic arithmetic operations and ensures the problem stays manageable. Simplifying at each step helps prevent mistakes and makes it easier to understand the process.

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Most popular questions from this chapter

Suppose that \(a\) continuous random variable has a joint probability density function given by $$f(x, y)=x^{2}+\frac{1}{3} x y, \quad 0 \leq x \leq 1, \quad 0 \leq y \leq 2$$. Find the probability that a point \((x, y)\) is in the region bounded by \(0 \leq x \leq \frac{1}{2}, 1 \leq y \leq 2,\) by evaluating the integral $$\int_{1}^{2} \int_{0}^{1 / 2} f(x, y) d x d y$$

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