Chapter 29: Problem 1
Evaluate the given functions. $$f(x, y)=3 x^{2} y-y^{3}, \text { find } f(-1,4) \text { and } f(2,-3)$$
Short Answer
Expert verified
\(f(-1,4) = -52\) and \(f(2,-3) = -9\).
Step by step solution
01
Plug in Values for First Set
Substitute the values \(x = -1\) and \(y = 4\) into the function \(f(x, y) = 3x^2y - y^3\).
02
Evaluate the Expression for First Set
Calculate \(3(-1)^2(4) - 4^3 = 3(1)(4) - 64 = 12 - 64 = -52\).
03
Plug in Values for Second Set
Substitute the values \(x = 2\) and \(y = -3\) into the function \(f(x, y) = 3x^2y - y^3\).
04
Evaluate the Expression for Second Set
Calculate \(3(2)^2(-3) - (-3)^3 = 3(4)(-3) + 27 = -36 + 27 = -9\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Function Evaluation
Function evaluation is the process of determining the output of a multivariable function given specific input values. In this exercise, we are given a function of two variables, \( f(x, y) = 3x^2y - y^3 \), and we need to find its value for certain inputs.
To evaluate a function:
To evaluate a function:
- Identify the variables in the function, here being \(x\) and \(y\).
- Replace these variables with the given numbers.
- Use algebraic operations to simplify and find the result.
Step-by-Step Solution
Step-by-step solutions make complex problems easier by breaking them down into manageable parts.
For instance, in evaluating the function \( f(x, y) = 3x^2y - y^3 \) at specific points, we evaluate each input separately.
For instance, in evaluating the function \( f(x, y) = 3x^2y - y^3 \) at specific points, we evaluate each input separately.
- Step 1 substitutes \( x = -1 \) and \( y = 4 \) into the function, replacing \(x\) and \(y\) in the expression.
- Step 2 calculates the expression: using simple arithmetic, determining that \( f(-1, 4) = -52 \).
- Step 3 substitutes \( x = 2 \) and \( y = -3 \).
- Step 4 simplifies this expression to find \( f(2, -3) = -9 \).
Algebraic Substitution
Algebraic substitution is a pivotal technique used in function evaluation and problem-solving. It involves replacing variables in a mathematical expression with specific values.
In our problem, the substitution of \( x = -1 \), \( y = 4 \) and \( x = 2 \), \( y = -3 \) into the function \( f(x, y) = 3x^2y - y^3 \) helps determine the function's output for these exact inputs.
This method:
In our problem, the substitution of \( x = -1 \), \( y = 4 \) and \( x = 2 \), \( y = -3 \) into the function \( f(x, y) = 3x^2y - y^3 \) helps determine the function's output for these exact inputs.
This method:
- Transforms abstract expressions into numerical calculations.
- Facilitates checking of solutions by easily substituting different values.
- Helps understand the effect of variables on the outcome.
Mathematical Expressions
Mathematical expressions combine numbers, variables, and operators to describe a specific quantity or relationship.
In the given function \( f(x, y) = 3x^2y - y^3 \), each component plays a role:
In the given function \( f(x, y) = 3x^2y - y^3 \), each component plays a role:
- The term \( 3x^2y \) indicates a multiplication of squares and linear terms, transforming with different \(x, y\) values.
- \(-y^3\) represents a cubic transformation, typically growing larger in magnitude faster than linear terms.