Chapter 12: Problem 40
Expand and simplify the rule of the function \(g .\) $$f(x)=2 x^{3}+3 x^{2}+x \text { and } g(x)=f(x-1)$$
Short Answer
Expert verified
Answer: The expanded and simplified expression for g(x) is g(x) = 2x^3 - 3x^2 + x.
Step by step solution
01
Substituting (x-1) into f(x)
To find the function \(g(x)\), we need to substitute \((x-1)\) into \(f(x)\). That means wherever we see an \(x\) in the function \(f(x)\), we will replace it with \((x-1)\). So,
$$g(x) = f(x-1) = 2(x-1)^3 + 3(x-1)^2 + x - 1$$
02
Expanding (x-1) terms
Now, we need to expand the cubes and squares of \((x-1)\) terms. Using the binomial theorem, we can expand \((x-1)^3\) and \((x-1)^2\) as follows:
$$(x-1)^3 = x^3 - 3x^2 + 3x - 1$$
$$(x-1)^2 = x^2 - 2x + 1$$
03
Substitute the expanded terms into g(x)
Now that we have the expanded forms of \((x-1)^3\) and \((x-1)^2\), we can substitute them back into the expression for \(g(x)\):
$$g(x) = 2(x^3 - 3x^2 + 3x - 1) + 3(x^2 - 2x + 1) + x - 1$$
04
Distribute the constants in g(x)
Now, we need to distribute the constants 2 and 3 in the expression of \(g(x)\). This will give us:
$$g(x) = 2x^3 - 6x^2 + 6x - 2 + 3x^2 - 6x + 3 + x - 1$$
05
Combine like terms
Finally, let's combine the like terms in the expression of \(g(x)\) to simplify it:
$$g(x) = 2x^3 - 6x^2 + 3x^2 + 6x - 6x + x - 2 + 3 - 1$$
$$g(x) = 2x^3 - 3x^2 + x$$
So, the expanded and simplified expression for \(g(x)\) is:
$$g(x) = 2x^3 - 3x^2 + x$$
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Polynomial Functions
A polynomial function is a mathematical expression consisting of variables and coefficients, structured in a form where non-negative integer powers of the variable are used. In the function \( f(x) = 2x^3 + 3x^2 + x \), we have a cubic polynomial, which means the highest degree of any term is 3. Each term in a polynomial can be characterized by:
- its coefficient - for instance, 2 in \(2x^3\),
- its base - which is the variable \(x\), and
- its exponent - which represents the power or degree of the term, such as 3 in \(x^3\).
Binomial Theorem
The Binomial Theorem is a powerful algebraic tool that provides a method for expanding expressions that are raised to a power, such as \((x - 1)^3\). It states that \((a + b)^n\) can be expanded as:\[\sum_{k=0}^{n} \binom{n}{k} a^{n-k} b^k\]This formula incorporates binomial coefficients \(\binom{n}{k}\), which can be found using Pascal's Triangle or calculated as\(\frac{n!}{k!(n-k)!}\). For example, when applying the binomial theorem to expand \((x-1)^3\), we calculate:
- \(x^3\) \((k=0)\)
- \(-3x^2\) \((k=1)\)
- \(+3x\) \((k=2)\)
- \(-1\) \((k=3)\)
Algebraic Expressions
Algebraic expressions are combinations of variables, numbers, and operations that represent mathematical relationships. In this exercise, we worked with the expression \[g(x) = 2x^3 - 6x^2 + 3x^2 + 6x - 6x + x - 2 + 3 - 1\], which was derived during the process of expanding \(f(x-1)\). When simplifying an algebraic expression:
- Identify like terms - terms that have the same variable part and exponent.
- Combine like terms by adding or subtracting coefficients.
Function Composition
Function composition involves creating a new function by applying one function to the results of another. In our exercise, the function \(g(x)\) is defined as \(f(x-1)\). This is an example of function composition, where we input \((x-1)\) instead of \(x\) into the function \(f\). Function composition allows:
- Modification of existing functions to shift, scale, or transform them.
- Building more complex functions from simpler ones.