Chapter 7: Problem 12
Determine whether each equation represents direct, inverse, joint, or combined variation. $$ y=2 x^{3} $$
Short Answer
Expert verified
Direct Variation.
Step by step solution
01
Understand the Types of Variation
There are four main types of variation: direct, inverse, joint, and combined. Direct variation is when one variable is a constant multiple of another (i.e., y = kx). Inverse variation is when one variable is a constant multiple of the reciprocal of another (i.e., y = k/x). Joint variation is when a variable varies directly as the product of two or more other variables (i.e., y = kxz). Combined variation involves both direct and inverse variations in the same equation.
02
Analyze the Given Equation
Look at the given equation: \( y = 2x^3 \). Notice that the equation relates \( y \) and \( x \) directly with a constant 2 and an exponent 3.
03
Determine the Type of Variation
Since the equation \( y = 2x^3 \) shows \( y \) directly proportional to \( x^3 \), it is a form of direct variation where the constant of proportionality is 2 and the exponent is 3.
04
Conclusion
Therefore, the equation \( y = 2x^3 \) represents direct variation.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Direct Variation
Direct variation occurs when one variable is a constant multiple of another, represented by the equation \( y = kx \), where \( k \) is the constant of proportionality. In simpler terms, if you double one variable, the other variable doubles too.
For example:
For example:
- The equation \( y = 5x \) shows direct variation, where \( k = 5 \).
- If \( y = 2x^3 \), it still represents direct variation because \( y \) is directly proportional to \( x^3 \). In this case, the constant of proportionality is 2, and the relationship involves an exponent.
Inverse Variation
Inverse variation happens when one variable is a constant multiple of the reciprocal of another, expressed as \( y = \frac{k}{x} \), where \( k \) is the constant of proportionality. In this type of variation, if one variable increases, the other variable decreases.
For example:
For example:
- In the equation \( y = \frac{10}{x} \), if \( x \) doubles, \( y \) is halved, demonstrating inverse variation.
- Another example is \( y = \frac{3}{x^2} \); as \( x \) increases, \( y \) decreases, but the relationship involves \( x^2 \).
Joint Variation
Joint variation is when a variable varies directly as the product of two or more variables. The general form is \( y = kxz \), where \( k \) is a constant of proportionality. Here, if either \( x \) or \( z \) increases, \( y \) increases.
Examples include:
Examples include:
- In the equation \( y = 2xz \), if \( x \) or \( z \) doubles, then \( y \) also doubles.
- Another example is \( y = kx^2z \), where \( y \) changes jointly with \( x^2 \) and \( z \).
Combined Variation
Combined variation involves both direct and inverse variations in the same equation. This means a variable depends on multiple factors that vary in different ways. An example form is \( y = \frac{kx}{z} \), where \( k \) is a constant.
Examples include:
Examples include:
- The equation \( y = \frac{4x}{z} \) shows that \( y \) varies directly with \( x \) and inversely with \( z \).
- Another example is \( y = \frac{kx^2}{w} \, where \) y varies directly with \( x^2 \) and inversely with \( w \).