Chapter 11: Problem 4
Let \(g(x, y, z)=x^{3} y^{2} z \sqrt{10-x-y-z}\) (a) Evaluate \(g(1,2,3)\) . (b) Find and describe the domain of \(g .\)
Short Answer
Expert verified
(a) 24; (b) Domain is all real numbers (x, y, z) such that \(x+y+z \leq 10\).
Step by step solution
01
Evaluate Specific Values
First, we need to substitute the values of \(x=1\), \(y=2\), and \(z=3\) into the function \(g(x, y, z)\). This gives us:\[g(1, 2, 3) = 1^{3} \cdot 2^{2} \cdot 3 \cdot \sqrt{10-1-2-3}\]
02
Simplify Exponents and Multiply
Calculate each part separately. Compute \(1^3 = 1\), \(2^2 = 4\), and multiply with \(3\):\[1 \cdot 4 \cdot 3 = 12\]
03
Calculate Inside the Square Root
Now, calculate the expression inside the square root:\[10 - 1 - 2 - 3 = 4\]
04
Square Root Calculation
Next, take the square root of the result:\[\sqrt{4} = 2\]
05
Final Multiplication
Finally, multiply the results obtained in previous steps:\[g(1, 2, 3) = 12 \cdot 2 = 24\]
06
Define Domains
Identify the constraints for the domain of the function given by the square root:The inside of the square root must be non-negative.\[10 - x - y - z \geq 0\]
07
Express Domain with Inequality
Rearrange to find the allowed set of values for \(x, y, z\):\[x + y + z \leq 10\]
08
Consider Variables Restrictions
Additionally, since the variables appear in the expression \(x^3y^2z\), all variables should be real numbers. There are inherently no restrictions beyond the interval mentioned except to ensure they remain real (excluding negatives in this context).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Domain of a Function
Understanding the domain of a multivariable function is crucial for identifying the set of all possible input values for which the function is defined. In the function \(g(x, y, z) = x^3 y^2 z \sqrt{10-x-y-z}\), the domain is determined by the condition inside the square root. This condition must be such that the expression inside remains non-negative:
- This means \(10 - x - y - z \geq 0\), ensuring the square root is real and non-negative.
- Therefore, we rearrange the inequality to \(x + y + z \leq 10\).
Function Evaluation
Evaluating a multivariable function means finding its output by substituting specific values for its variables. We're given the function \(g(x, y, z)\) to evaluate at \((1, 2, 3)\). Here’s a simple walkthrough:
- First, substitute the values: \(g(1, 2, 3) = 1^3 \cdot 2^2 \cdot 3 \cdot \sqrt{10-1-2-3}\).
- Calculate each part step by step. \(1^3 = 1\) and \(2^2 = 4\), leading to \(1 \times 4 \times 3 = 12\).
- Evaluate the square root expression by calculating \(10 - 1 - 2 - 3 = 4\), thus \(\sqrt{4} = 2\).
- Finally, multiply the computed values: \(12 \times 2 = 24\).
Understanding the Square Root
The square root operation is fundamental in mathematics, especially in functions involving radicals. In the function \(g(x, y, z)\), the square root \(\sqrt{10-x-y-z}\) imposes a significant constraint. Here's why it matters:
- The expression inside the square root, \(10-x-y-z\), must be non-negative for the square root to be defined in the real number system.
- A negative value under the square root would yield an imaginary number, which is typically outside the scope for real-valued functions unless specifically stated.
- Understanding this constraint helps in determining the domain of the function, ensuring all operations remain valid for real numbers.