Chapter 4: Problem 71
Suppose \(u\) and \(v\) belong to a vector space \(V\). Simplify each of the following expressions: (a) \(E_{1}=4(5 u-6 v)+2(3 u+v)\), (c) \(E_{3}=6(3 u+2 v)+5 u-7 v\), (b) \(E_{2}=5(2 u-3 v)+4(7 v+8)\), (d) \(E_{4}=3(5 u+2 / v)\).
Short Answer
Expert verified
The simplified expressions are:
(a) \( E_{1}= 26u - 22v \)
(b) \( E_{2}= 10u + 13v + 32 \)
(c) \( E_{3}= 23u + 5v \)
(d) \( E_{4}= 15u + \frac{6}{v} \)
Step by step solution
01
Distribute the scalar to each vector term
Multiply each scalar (4 and 2) by the corresponding vector terms:
\( E_{1}= (4 \cdot 5)u - (4 \cdot 6)v + (2 \cdot 3)u + 2v \)
02
Simplify the scalar-vector multiplication
Simplify the multiplication:
\( E_{1}= 20u - 24v + 6u + 2v \)
03
Combine like terms
Combine the terms that correspond to the same vector:
\( E_{1}= (20u + 6u) + (-24v + 2v) = 26u - 22v \)
(b) \( E_{2}=5(2 u-3 v)+4(7 v+8) \)
04
Distribute the scalar to each vector term
Multiply each scalar (5 and 4) by the corresponding vector terms:
\( E_{2}= (5 \cdot 2)u - (5 \cdot 3)v + (4 \cdot 7)v + (4 \cdot 8) \)
05
Simplify the scalar-vector multiplication
Simplify the multiplication:
\( E_{2}= 10u - 15v + 28v + 32 \)
06
Combine like terms
Combine the terms that correspond to the same vector:
\( E_{2}= 10u + (-15v + 28v) + 32 = 10u + 13v + 32 \)
(c) \( E_{3}=6(3 u+2 v)+5 u-7 v \)
07
Distribute the scalar to each vector term
Multiply the scalar (6) by the corresponding vector terms:
\( E_{3}= (6 \cdot 3)u + (6 \cdot 2)v + 5u - 7v \)
08
Simplify the scalar-vector multiplication
Simplify the multiplication:
\( E_{3}= 18u + 12v + 5u - 7v \)
09
Combine like terms
Combine the terms that correspond to the same vector:
\( E_{3}= (18u + 5u) + (12v - 7v) = 23u + 5v \)
(d) \( E_{4}=3(5 u+2 / v) \)
10
Distribute the scalar to each vector term
Multiply the scalar (3) by the corresponding vector terms:
\( E_{4}= (3 \cdot 5)u + (3 \cdot \frac{2}{v}) \)
11
Simplify the scalar-vector multiplication
Simplify the multiplication:
\( E_{4}= 15u + \frac{6}{v} \)
In conclusion, the simplified expressions are:
(a) \( E_{1}= 26u - 22v \)
(b) \( E_{2}= 10u + 13v + 32 \)
(c) \( E_{3}= 23u + 5v \)
(d) \( E_{4}= 15u + \frac{6}{v} \)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Scalar Multiplication
In the context of vector spaces, scalar multiplication is a fundamental operation. It involves multiplying a vector by a scalar (a real number). The result is a new vector that points in the same or opposite direction as the original vector but has its magnitude scaled by the factor of the scalar. For instance, considering a scalar multiplication like \(4(5u - 6v)\), you multiply each element inside the parenthesis by 4. The expression becomes \(20u - 24v\). Here, both vectors \(u\) and \(v\) are scaled individually.
Some important points about scalar multiplication are:
Some important points about scalar multiplication are:
- Scalar multiplication is commutative and associative. This means \(a(bu) = (ab)u\).
- If a scalar is zero, the resulting vector is a zero vector, regardless of the original vector.
- Scalar multiplication does not change the vector's direction if multiplied by a positive scalar.
Vector Addition
Vector addition is another crucial concept in vector spaces. It involves adding two vectors to create a resultant vector. The operation is straightforward: add each corresponding component of the vectors. For example, consider combining like terms in the expression \(26u - 22v\). This step is essential in simplifying computations involving multiple vectors.
Here's how vector addition works:
Here's how vector addition works:
- The addition is conducted by summing up corresponding components, maintaining the dimension of the vectors.
- Vector addition is both commutative: \(u + v = v + u\), and associative: \(u + (v + w) = (u + v) + w\).
- Adding a zero vector leaves the vector unchanged: \(u + 0 = u\).
Linear Combinations
In vector spaces, a linear combination refers to an expression made up of vectors and scalars. This combination involves both operations—scalar multiplication and vector addition. The expressions \(E_1 = 4(5u - 6v) + 2(3u + v)\) and \(E_3 = 6(3u + 2v) + 5u - 7v\) are modifications using linear combinations of the vectors \(u\) and \(v\). This type of expression helps describe any vector in terms of other vectors.
Linear combinations cover a few key characteristics:
Linear combinations cover a few key characteristics:
- A linear combination is "linear" because it involves no powers or products of the involved vectors.
- They play a central role in defining vector spaces, allowing for linear dependencies and independencies.
- Any vector in a vector space can be expressed as a linear combination of a set of basis vectors.