Chapter 9: Problem 1
Let \(T: \mathbb{P}_{2} \rightarrow \mathbb{R}\) be a linear transformation such that $$ T\left(x^{2}\right)=1 ; T\left(x^{2}+x\right)=5 ; T\left(x^{2}+x+1\right)=-1 $$ Find \(T\left(a x^{2}+b x+c\right)\)
Short Answer
Expert verified
T(ax^2 + bx + c) = a + 4b - 6c
Step by step solution
01
- Understand the Linear Transformation
Given that T is a linear transformation, recall that for any polynomials P(x) and Q(x) and scalars a and b, the following property holds: T(aP(x) + bQ(x)) = aT(P(x)) + bT(Q(x)).
02
- Express the Polynomial
The polynomial given is ax^2 + bx + c. This can be broken down as follows: ax^2 + bx + c = a(x^2) + b(x) + c(1). By linearity, we need to determine T(ax^2 + bx + c).
03
- Use Given Transformations
Using the given transformations, T(x^2) = 1, T(x^2 + x) = 5, and T(x^2 + x + 1) = -1, express T(x) and T(1) in terms of these. First, we compute T(1) and T(x):
04
- Compute T(1)
We know from T(x^2 + x + 1) = -1 and the previous transformations that T(x^2) + T(x) + T(1) = -1. Substitute T(x^2) = 1 and T(x^2 + x) = 5, solve for T(1):
05
- Solve for T(1)
\[ 1 + T(x) + T(1) = -1 \]
06
- Simplify Equation
We also know that T(x^2 + x) = T(x^2) + T(x) = 5. Thus, T(x) = 4. Substitute T(x) to solve for T(1):
07
- Solve for T(1)
1 + 4 + T(1) = -1. Simplifying gives T(1) = -6.
08
- Apply Linearity
Now, apply linearity to find T(ax^2 + bx + c):
09
- Compute Final Expression
T(ax^2 + bx + c) = aT(x^2) + bT(x) + cT(1). Substitute the known values:
10
- Simplify Final Expression
\[ T(ax^2 + bx + c) = a(1) + b(4) + c(-6) \]
11
- Final Result
Simplify to get the final answer: \[ T(ax^2 + bx + c) = a + 4b - 6c \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Polynomial Expression
A polynomial expression is a mathematical expression involving a sum of powers in one or more variables multiplied by coefficients. In this exercise, we deal with a polynomial of the form (ax^2 + bx + c). Here:
- 'a', 'b', and 'c' are the coefficients.
- 'x' is the variable, and
- The highest power of 'x' is 2, making this a second-degree polynomial.
- The term 'ax^2' is a degree-2 term.
- The term 'bx' is a degree-1 term.
- 'c' is a constant (degree-0 term).
Linearity Property
The linearity property of a transformation is crucial. It tells us how to deal with sums and scalar multiples of functions. A transformation T is linear if for any two polynomials P(x) and Q(x) and scalars a and b, the following holds: \[T(aP(x) + bQ(x)) = aT(P(x)) + bT(Q(x))\] This property allows us to handle complex polynomials systematically by breaking them into simpler parts. For the given problem, this means we express the polynomial ax^2 + bx + c as a combination of simpler polynomials:
- \[ax^2\]
- \[bx\]
- \[c\]
- \(T(ax^2 + bx + c) = aT(x^2) + bT(x) + cT(1)\)
Transformation Computation
Using the given transformations and applying linearity, we can compute the necessary values to transform any polynomial of the form ax^2 + bx + c. Here's how we proceed:
Given transformations:
\[1 + T(x) + T(1) = -1\] Solving step-by-step, we find:
\[T(x) = 4\]
\[1 + 4 + T(1) = -1\] so, ### Final Expression for Polynomial Transformation With the values of T(x) and T(1) identified, we use linearity to find:
\[T(ax^2 + bx + c) = aT(x^2) + bT(x) + cT(1)\]
By substituting known values:
\left( \[T(ax^2 + bx + c) = a(1) + b(4) + c(-6)\] \right) Slowing down for simplification, we get:
\[T(ax^2 + bx + c) = a + 4b - 6c\]
So, the transformed polynomial is T(ax^2 + bx + c), in the form: \[a + 4b - 6c\]
Given transformations:
- \(T(x^2) = 1\)
- \(T(x^2 + x) = 5\)
- \(T(x^2 + x + 1) = -1\)
- Identify relationships from the given transformations.
- Calculate unknown values like T(x) and T(1).
\[1 + T(x) + T(1) = -1\] Solving step-by-step, we find:
\[T(x) = 4\]
\[1 + 4 + T(1) = -1\] so, ### Final Expression for Polynomial Transformation With the values of T(x) and T(1) identified, we use linearity to find:
\[T(ax^2 + bx + c) = aT(x^2) + bT(x) + cT(1)\]
By substituting known values:
\left( \[T(ax^2 + bx + c) = a(1) + b(4) + c(-6)\] \right) Slowing down for simplification, we get:
\[T(ax^2 + bx + c) = a + 4b - 6c\]
So, the transformed polynomial is T(ax^2 + bx + c), in the form: \[a + 4b - 6c\]