Chapter 8: Problem 75
Let \(f(x)=-2 x+5 .\) For what value of \(x\) does function \(f\) have the given value? See Example 5. $$ f(x)=5 $$
Short Answer
Expert verified
The value of \(x\) is 0.
Step by step solution
01
Understanding the Equation
The problem gives us a function \(f(x) = -2x + 5\) and tells us that the function has a value of 5. This means that we need to solve the equation \(f(x) = 5\) to find the value of \(x\). In mathematical terms, this is written as \(-2x + 5 = 5\).
02
Setting Up the Equation
First, write the equation with the given function value plugged in: \(-2x + 5 = 5\). This equation needs to be solved to find \(x\).
03
Isolating the Variable Term
Subtract 5 from both sides of the equation to help isolate the term containing \(x\): \(-2x + 5 - 5 = 5 - 5\). This simplifies to \(-2x = 0\).
04
Solving for \(x\)
Divide each side of the equation by \(-2\) to solve for \(x\). So, \(x = \frac{0}{-2}\). This simplifies to \(x = 0\).
05
Verification
Substitute \(x = 0\) back into the original function to check: \(f(0) = -2(0) + 5 = 5\). Since this equals the given function value, our solution is verified.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Function Evaluation
In the context of algebra, evaluating a function is a crucial technique that helps us determine the output of a function for a specific input. A function, like the one given in the problem, is generally written as:
- Function notation: An example is \(f(x) = -2x + 5\)
Here, \(f\) represents the function, and \(x\) is the input variable.
Solving Linear Equations
Linear equations are equations that make a straight line when graphed and are usually expressed as \(ax + b = c\), where \(a\), \(b\), and \(c\) are constants. To solve a linear equation for \(x\), the goal is to isolate \(x\) on one side of the equation. This involves a few key steps:
- Step 1: Simplify each side of the equation if necessary.
- Step 2: Move terms involving \(x\) to one side and constant terms to the other.
In our case, after setting the function equal to 5, we have the equation: \(-2x + 5 = 5\). By subtracting 5 from both sides, we start the isolation process. - Step 3: Solve for \(x\) by dividing by the coefficient of \(x\).
Here, \(-2x = 0\), and dividing both sides by \(-2\) gives \(x = 0\).
Verification of Solutions
Verification is a vital part of solving equations, ensuring that the solution we found is indeed correct. After solving for \(x\), we should substitute it back into the original function to confirm:
- Substitution Method: Replace the variable \(x\) in the original function with the solution value.
Given our solution \(x = 0\), plug it into the function \(f(x) = -2x + 5\) to check if it results in the given function value of 5.