Question

What is the value of \(f(-2)\) if \(f(x)=\frac{x^2+4 x-8}{x-2}\) ? A) \(-3\) B) \(-1\) C) 1 D) 3

Short answer

D) 3

Step-by-step solution

Substitute x with -2

First, we need to replace x with -2 in the function. The function is given as: \(f(x) = \frac{x^2 + 4x - 8}{x - 2}\). So, plugging -2 into the function, we get: \[f(-2) = \frac{(-2)^2 + 4(-2) - 8}{(-2) - 2}\] Step 2: Simplify the expression

Simplify the expression

Now let's simplify the expression. In the numerator, we have: \((-2)^2 = 4\), \(4(-2) = -8\), and \(4 - 8 - 8 = -12\). In the denominator, we have: \((-2) - 2 = -4\). So we get: \[f(-2) = \frac{-12}{-4}\] Step 3: Final simplification and find the value

Final simplification and find the value

Finally, let's simplify the expression by dividing -12 by -4 and find the value of f(-2). \[f(-2) = \frac{-12}{-4} = 3\] So, the value of f(-2) = 3. The correct answer is D) 3.

Key concepts

Substitution Method

The substitution method is a straightforward approach in algebra, used to simplify functions by replacing variables with specific values. In this exercise, our task is to determine the value of the function \(f(x)\) at \(x = -2\). By substituting \(-2\) into the function \(f(x) = \frac{x^2 + 4x - 8}{x - 2}\), we can simplify and solve for \(f(-2)\). This methodical replacement of \(x\) helps us focus on evaluating the function without changing its structure.

• Choose the specific value for \(x\) to evaluate the function at that point.
• Replace all instances of \(x\) in the function with the chosen value.
• Proceed to simplify the resulting expression.

Substitution requires careful arithmetic to ensure each replacement and calculation is accurate. It forms the foundation of solving many algebraic problems.

Expression Simplification

Expression simplification is essential for solving algebraic equations, providing a clear and concise form of the problem before further calculations. In our exercise, once \(x = -2\) is substituted into the function \(f(x) = \frac{x^2 + 4x - 8}{x - 2}\), simplifying becomes the next step.

• Begin by simplifying the numerator. Replace \((-2)^2\) with 4, compute \(4(-2)\) as -8, and sum these with the constant -8 to complete the numerator as -12.
• Simplify the denominator by calculating \((-2) - 2\), resulting in -4.

After simplification, we transform the entire function into \(f(-2) = \frac{-12}{-4}\). This clear, reduced form is simpler to evaluate and helps in finding the function value.

Numerator and Denominator

In algebraic functions, understanding the roles of the numerator and denominator is crucial in both simplifying and evaluating the function. The numerator of a fraction contains the expression above the dividing line, while the denominator contains the expression below it. Adjusting these parts carefully allows us to simplify the expression efficiently. In our function \( f(x) = \frac{x^2 + 4x - 8}{x-2} \), evaluating the numerator involves arithmetic operations on \((-2)^2\), \(4(-2)\), and -8, resulting in a total of -12. The denominator calculation \((-2) - 2\) is -4.

• The numerator, \(-12\), represents the total after simplifying expressions and combining constants.
• A non-zero denominator, in our case \(-4\), is crucial to avoid undefined expressions.

This step ensures that the fraction can properly simplify without errors, yielding \(f(-2) = \frac{-12}{-4}\), a valid algebraic expression for evaluation.

Function Evaluation

Function evaluation brings clarity to abstract algebraic functions by finding their numerical values at specific points. After substituting and simplifying, the final task is evaluating the function. Our calculated expression \(f(-2) = \frac{-12}{-4}\) must be reduced by performing the division.

• Take \(-12\), the result from the numerator, and divide by \(-4\), the result from the denominator.
• This division simplifies to 3, providing a concrete value that \(f(x)\) returns when \(x = -2\).

Function evaluation is important because it transforms abstract expressions into concrete outcomes. Here, it shows that at \(x = -2\), the function \(f(x)\) attends a numerical value of 3, confirming that our calculations align with the given solution.