Chapter 1: Problem 57
Find \(f(x)\) at the indicated value of \(x\). $$f(x)=-x^{2}+x+2 ; x=4$$
Short Answer
Expert verified
\( f(4) = -10 \)
Step by step solution
01
Identify the Function and Value
The function provided is \( f(x) = -x^2 + x + 2 \). We are given \( x = 4 \) and need to evaluate the function at this specific point.
02
Substitute x with 4
Replace \( x \) with 4 in the function. This gives us \( f(4) = -(4)^2 + 4 + 2 \).
03
Simplify the Squared Term
Calculate \( (4)^2 \), which equals 16. Substitute this back into the equation: \( f(4) = -16 + 4 + 2 \).
04
Perform the Addition and Subtraction
First, add 4 and 2 together to get 6. Then subtract 16 from this result: \( f(4) = 6 - 16 \).
05
Calculate the Final Result
Finally, perform the subtraction: \( 6 - 16 = -10 \). This means \( f(4) = -10 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Substitution
Substitution is a fundamental process in mathematics where we replace a variable with a specific value. In this exercise, we start with the quadratic function \(f(x) = -x^2 + x + 2\). Here, our goal is to find the value of \(f(x)\) when \(x = 4\).
To do this, we take every occurrence of \(x\) in the function and substitute it with 4.
To do this, we take every occurrence of \(x\) in the function and substitute it with 4.
- First, identify the function: \(f(x) = -x^2 + x + 2\).
- Then substitute: \(f(4) = -(4)^2 + 4 + 2\).
- Remember: Substitution is simply about plugging in the number given for \(x\) into the function.
Simplification
Simplification is a method we use to make mathematical expressions easier to work with. After substituting \(x = 4\) into our function, we have \(f(4) = -(4)^2 + 4 + 2\). The next step involves simplification to get a final result. Here's a closer look:
- First, calculate \((4)^2\), which equals 16. Then substitute this back: \(f(4) = -16 + 4 + 2\).
- Now, it's about performing operations in the correct order:
- First, add the numbers: 4 + 2 = 6.
- Then, perform the subtraction: 6 - 16 = -10.
Quadratic Function
A quadratic function is an important algebraic concept characterized by the general form \(ax^2 + bx + c\), where \(a\), \(b\), and \(c\) are constants. Our example function \(f(x) = -x^2 + x + 2\) fits this form well:
- The term \(-x^2\) is known as the quadratic term and it determines the "U" shaped curve of the parabola. The negative sign in front indicates the parabola opens downwards.
- The linear term, \(x\), affects the slope or tilt of the parabola.
- Finally, the constant term, \(+2\), shifts the parabola vertically.