Chapter 4: Problem 8
If \(f(a)=a^{2}-12\), what is \(f(b-a) ?\) (A) \(a^{2}+b^{2}-12\) (B) \(a^{3}-b-12\) (C) \(a^{2}-2 a b-b^{2}-12\) (D) \(a^{2}-2 a b+b^{2}-12\)
Short Answer
Expert verified
The answer is (D) \(a^{2}-2ab+b^{2}-12\).
Step by step solution
01
Identify the Expression
We need to evaluate the expression given by the function \( f \) at \( b-a \). Thus, we want to calculate \( f(b-a) \).
02
Use the Definition of the Function
Given that \( f(x) = x^2 - 12 \), substitute \( x = b-a \) to find \( f(b-a) \). This means we need \( (b-a)^2 - 12 \).
03
Expand \((b-a)^2\)
Apply the formula for the square of a binomial: \((b-a)^2 = b^2 - 2ab + a^2\). We have expanded \((b-a)^2\) into terms that we can substitute back into our function.
04
Substitute and Simplify
Substitute \( (b-a)^2 = b^2 - 2ab + a^2 \) into \( f(b-a) \), resulting in \( b^2 - 2ab + a^2 - 12 \). The expression simplifies to \( a^2 - 2ab + b^2 - 12 \), which matches option (D).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Functions and Expressions
In mathematics, a function is a special kind of relation that assigns each input exactly one output. Functions are usually written as \( f(x) \), where \( x \) is the input, and \( f(x) \) is the output. For example, in the problem given, we have the function \( f(a) = a^2 - 12 \). Here, \( a \) represents the input, and \( a^2 - 12 \) is what comes out after applying the function to \( a \).
Expressions, on the other hand, are combinations of numbers, variables, and arithmetic operations. They do not have an equal sign. In the function \( f(a) = a^2 - 12 \), the expression part is \( a^2 - 12 \). This tells us what calculations are performed using the input \( a \).
When dealing with functions and expressions, it helps to understand how to substitute values and simplify them:
Expressions, on the other hand, are combinations of numbers, variables, and arithmetic operations. They do not have an equal sign. In the function \( f(a) = a^2 - 12 \), the expression part is \( a^2 - 12 \). This tells us what calculations are performed using the input \( a \).
When dealing with functions and expressions, it helps to understand how to substitute values and simplify them:
- Substitute given values into the function in place of the variable.
- Manipulate expressions according to algebraic rules to simplify or find specific values.
Exploring Binomial Expansion
Binomial expansion is a method used to expand an expression that raises a binomial to a power. A binomial is an algebraic expression containing two distinct terms. In the exercise, the expression \((b-a)^2\) is an example of a binomial where binomial expansion is applied.
When expanding \((b-a)^2\), you apply the formula \((b-a)^2 = b^2 - 2ab + a^2\). Each term in the expansion represents how parts of the binomial multiply together.
When expanding \((b-a)^2\), you apply the formula \((b-a)^2 = b^2 - 2ab + a^2\). Each term in the expansion represents how parts of the binomial multiply together.
- \(b^2\) comes from multiplying \(b\) by itself.
- \(-2ab\) comes from two instances of \(b \times -a\).
- \(a^2\) comes from multiplying \(-a\) by itself.
Mastering Algebraic Manipulation
Algebraic manipulation involves rearranging expressions using basic algebraic rules to solve equations or simplify expressions. This is a crucial skill in solving math problems.
In the problem provided, after expanding the binomial, we need to substitute the expanded expression back into the function. The process involves:
In the problem provided, after expanding the binomial, we need to substitute the expanded expression back into the function. The process involves:
- Substituting \((b-a)^2\) with its expanded form \(b^2 - 2ab + a^2\).
- Integrating the new expression into the function \(f(b-a) = (b-a)^2 - 12\).
- Simplifying to get \(a^2 - 2ab + b^2 - 12\), which matches the correct answer choice.