Chapter 10: Problem 2
In Problems 1-14, use the properties of limits to calculate the following limits: $$ \lim _{(x, y) \rightarrow(-1,1)}\left(2 x y+3 x^{2}\right) $$
Short Answer
Expert verified
The limit is 1.
Step by step solution
01
Identify the Limit Expression
We need to calculate the limit of the expression \( 2xy + 3x^2 \) as \((x, y)\) approaches \((-1, 1)\). First, recognize that this is a polynomial expression, involving \(x\) and \(y\).
02
Apply the Direct Substitution Property
Since the expression \(2xy + 3x^2\) is a polynomial, limits can be directly substituted according to the limit properties for polynomials. Substitute \(x = -1\) and \(y = 1\) into the expression.
03
Evaluate the Substituted Expression
Calculate the result of substituting the given coordinates into the polynomial. Substitute and compute: \(2(-1)(1) + 3(-1)^2\).
04
Simplify the Expression
Now, simplify the expression from Step 3. \(2(-1)(1) = -2\) and \(3(-1)^2 = 3\). Add these results: \(-2 + 3 = 1\).
05
State the Result of the Limit
The calculation results in \(1\). Therefore, the limit of the expression as \((x, y)\) approaches \((-1, 1)\) is 1.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Limits
Limits in calculus help us understand how a function behaves as its inputs approach a specific value. Imagine trying to find the value a function is "heading towards" without necessarily reaching it.
In this exercise, we aim to determine what happens to the function \(2xy + 3x^2\) as \((x, y)\) gets closer and closer to \((-1, 1)\).
In this exercise, we aim to determine what happens to the function \(2xy + 3x^2\) as \((x, y)\) gets closer and closer to \((-1, 1)\).
- A limit captures how output values of a function approach a single number as input variables get arbitrarily close to a specific point.
- This concept is crucial for calculus, particularly in the context of continuity and derivatives.
- Understanding and applying limits, like in our exercise, becomes easier when you know whether direct substitution can be applied or further manipulation is needed.
Polynomial Functions
Polynomial functions are a specific type of mathematical expression consisting of variables and coefficients. These expressions contain terms in the form of constants, powers, and their products. For example, \(2xy + 3x^2\) is a polynomial in terms of \(x\) and \(y\).
Key characteristics of polynomial functions include:
Key characteristics of polynomial functions include:
- They are composed of smooth, curved lines and can be of degree zero (constant) or higher for one or more variables.
- Polynomials are straightforward to work with because they are continuous everywhere and differentiable.
- Limits of polynomial functions, such as the one explored in our exercise, can typically be solved by substituting directly.
Direct Substitution Method
The direct substitution method is a straightforward approach recognized by its simplicity in solving limits when dealing with polynomial functions like the one in our example.
Here's how it works:
Here's how it works:
- If the function is polynomial and the variables approach a finite point, you can often substitute the values directly into the function.
- This approach relies on the property that polynomials are continuous, meaning their limits at any point correspond to their actual values at that point.
- In our specific exercise, substituting \(x = -1\) and \(y = 1\) directly into \(2xy + 3x^2\) produces a straightforward computation which can be simplified to find the limit.