Chapter 6: Problem 16
Let \(T: \mathscr{P}_{2} \rightarrow \mathscr{P}_{1}\) be a linear transformation for which \(T(1)=1+x, T(x)=3-2 x,\) and \(T\left(x^{2}\right)=4+3 x\) Find \(T\left(4-x+3 x^{2}\right)\) and \(T\left(a+b x+c x^{2}\right)\)
Short Answer
Expert verified
\(T(4-x+3x^2)=13+15x\) and \(T(a+bx+cx^2)=(a+3b+4c)+(a-2b+3c)x\).
Step by step solution
01
Identify Polynomial Transformation
We are asked to find the transformation \(T\) applied to the polynomial \(4-x+3x^2\). To do this, we can use linearity of the transformation.
02
Break Down the Expression
The transformation \(T\) is linear, so:\[T(4-x+3x^2) = T(4) + T(-x) + T(3x^2)\]We can further break this by expressing in terms of known transformations:\[ T(4) = 4 \cdot T(1), T(-x) = -1 \cdot T(x), T(3x^2) = 3 \cdot T(x^2)\]
03
Compute Each Component
Compute the transformation of each component using the given transformation rules:1. \(T(4) = 4(1+x) = 4 + 4x\)2. \(T(-x) = -1(3-2x) = -3 + 2x\)3. \(T(3x^2) = 3(4+3x) = 12 + 9x\)
04
Combine the Components
Sum these results together using the linearity property:\[T(4-x+3x^2) = (4 + 4x) + (-3 + 2x) + (12 + 9x)= 13 + 15x\]
05
Generalize for Any Polynomial
To find \(T(a + bx + cx^2)\), use linearity again:\[T(a + bx + cx^2) = aT(1) + bT(x) + cT(x^2)\]Substitute known values:1. \(aT(1) = a(1+x) = a + ax\)2. \(bT(x) = b(3-2x) = 3b - 2bx\)3. \(cT(x^2) = c(4 + 3x) = 4c + 3cx\)Combine the terms:\[T(a + bx + cx^2) = (a + 3b + 4c) + (a - 2b + 3c)x\]
06
Final Expression
For \(T(4-x+3x^2)\):\[T(4-x+3x^2) = 13 + 15x\]For \(T(a+b x+c x^{2})\):\[T(a+b x+c x^{2}) = (a + 3b + 4c) + (a - 2b + 3c)x\]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Polynomial Basis
In the realm of polynomial functions, the concept of a polynomial basis is a fundamental aspect that ensures any polynomial expression can be expressed uniquely. A polynomial in \( \mathscr{P}_n \) is typically expressed in the standard basis as \( a + bx + cx^2 + \cdots \) for a second-degree polynomial.
For a transformation like \( T: \mathscr{P}_2 \to \mathscr{P}_1 \), the polynomial basis plays a critical role. Here, the basis \( \{1, x, x^2\} \) is used for the domain of \( T \). This means that any polynomial can be written as a linear combination of these basis elements.
For a transformation like \( T: \mathscr{P}_2 \to \mathscr{P}_1 \), the polynomial basis plays a critical role. Here, the basis \( \{1, x, x^2\} \) is used for the domain of \( T \). This means that any polynomial can be written as a linear combination of these basis elements.
- The polynomial basis provides a framework to systematically categorize and solve polynomial problems.
- It ensures that polynomials can be manipulated and transformed accurately, as seen in our exercise with different polynomials like \( T(1), T(x), \) and \( T(x^2) \).
- This organization into a basis facilitates the computation involved in polynomial transformations.
Linearity Property
The linearity property of transformations is central to solving polynomial transformation problems. When we say a transformation \( T \) is linear, we mean that it satisfies two vital properties:
- Additivity: \( T(u + v) = T(u) + T(v) \) for any polynomials \( u \) and \( v \).
- Scalar Multiplication: \( T(cu) = cT(u) \) for a scalar \( c \).
- When transforming a polynomial like \( 4-x+3x^2 \), we can calculate \( T(4) \), \( T(-x) \), and \( T(3x^2) \) individually and simply add the results.
- This methodology uses the concept that each part of the polynomial is transformed independently and then combined, simplifying the calculation process.
Polynomial Transformation
Polynomial transformation is the process of applying a transformation function like \( T \) to polynomial expressions within a specified domain. In our exercise, we were tasked with finding the transformation of \(4-x+3x^2\) and \(a + bx + cx^2 \).
Transformations such as \( T \) modify polynomials based on a rule or set of rules.
Transformations such as \( T \) modify polynomials based on a rule or set of rules.
- Each term in the polynomial is treated according to the linear rules defined by the transformation function.
- When finding the transformation of general polynomials, \( T(a + bx + cx^2) \), we can systematically apply \( T(1), T(x), \) and \( T(x^2) \) to express the result in terms of known transformations.
- Transformations often convert complex polynomial expressions into simpler, more useful forms by leveraging the known values of basis transformations.