Chapter 3: Problem 9
Let \(x \Theta y=x \sqrt{y}-y-2 x\). For what value of \(x\) does \(x \Theta y=-y\) for all values of \(y\) ? (A) 0 (B) \(\frac{2}{\sqrt{3}}\) (C) \(\sqrt{3}\) (D) 2 (E) 4
Short Answer
Expert verified
The value of \( x \) is 0.
Step by step solution
01
Understand the Problem
We need to find the value of \( x \) such that the operation \( x \Theta y = x \sqrt{y} - y - 2x \) becomes \( -y \) for all values of \( y \). This means we have to solve the equation \( x \Theta y = -y \) for \( x \).
02
Set up the Equation
Start with the equation given by the problem: \( x \Theta y = -y \). Substituting the expression for \( x \Theta y \), we have: \( x \sqrt{y} - y - 2x = -y \).
03
Simplify the Equation
Cancel out \( -y \) from both sides of the equation: \( x \sqrt{y} - 2x = 0 \).
04
Factor and Solve the Equation
Factor out \( x \) from the equation \( x \sqrt{y} - 2x = 0 \): \( x(\sqrt{y} - 2) = 0 \). For this equation to hold for all \( y \), \( x = 0 \) or \( \sqrt{y} - 2 = 0 \).
05
Verify the Solution
Since \( x \) must be a constant that works for all values of \( y \), the only viable solution is \( x = 0 \), because \( \sqrt{y} - 2 = 0 \) does not hold for all \( y \). Thus, \( x = 0 \) is the solution.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Functions and Operations
Functions and operations in mathematics often involve applying a specific order or rule to one or more variables. In the given task, you encounter a custom operation denoted as \( x \Theta y = x \sqrt{y} - y - 2x \). This is not a standard function or operation you might be familiar with like addition or multiplication, but it follows a similar premise: you perform certain calculations on inputs \( x \) and \( y \). An important aspect of understanding functions and operations is recognizing how they transform inputs into outputs.Here are some key points:
- Operations: They are rules or procedures like addition, subtraction, etc., that combine one or more inputs to produce a result.
- Functions: They take inputs, usually called arguments, and apply a specific rule to get outputs.
- Custom Operations: Occasionally, you will encounter operations that are unique to a problem, like our \( x \Theta y \).
Algebraic Manipulation
Algebraic manipulation is a fundamental skill in solving equations. It involves rearranging terms and simplifying expressions to make equations more manageable or to isolate a specific variable. In our exercise, once we decide that \( x \Theta y = -y \) for all \( y \), we set up the equation:\[ x \Theta y = x \sqrt{y} - y - 2x = -y \]Here's the step-by-step breakdown of how manipulation helps:
- Canceling Terms: You notice there's \(-y\) on both sides of the equation. Simply subtract \(-y\) from each side to help simplify.
- Factoring: With \( x \sqrt{y} - 2x = 0 \), you can factor out common terms. In this case, factor out \( x \): \( x(\sqrt{y} - 2) = 0 \).
- Identifying Solutions: From the factored equation, recognize that for the equation to hold true regardless of \( y\), \( x \) must be zero. The other option, \( \sqrt{y} - 2 = 0 \), is not feasible for every \( y \).
Equation Solving
Solving equations is about finding the values of variables that make the equation true. In this problem, we're looking for a specific \( x \) that satisfies the equation \( x \Theta y = -y \) for all values of \( y \). This implies that the solution should not depend on the variable \( y \). Here's how you can think about it:
- Understanding Solutions: The goal is to find a constant value for \( x \) such that no matter what \( y \) is, the equation holds true.
- Factor Considerations: Once you factor the equation \( x(\sqrt{y} - 2) = 0\), you see two potential solutions: \( x = 0 \) or \( \sqrt{y} - 2 = 0 \).
- Feasibility: The solution \( \sqrt{y} - 2 = 0 \) would only be applicable for a specific, fixed \( y \), but since \( y \) is a variable that can take on any value, the first solution \( x = 0 \) fits since it doesn’t depend on \( y \).