Math Problem Statement

Express v = (-4, 7, 1) in R^3 as a linear combination of the vectors v1 = (0, 1, 1), v2 = (1, 2, -2), v3 = (3, 1, 0).

Solution

We are asked to express the vector v=(4,7,1)\mathbf{v} = (-4, 7, 1) as a linear combination of the vectors v1=(0,1,1)\mathbf{v_1} = (0, 1, 1), v2=(1,2,2)\mathbf{v_2} = (1, 2, -2), and v3=(3,1,0)\mathbf{v_3} = (3, 1, 0).

In other words, we need to find scalars aa, bb, and cc such that: v=av1+bv2+cv3\mathbf{v} = a \mathbf{v_1} + b \mathbf{v_2} + c \mathbf{v_3} This can be written as the following system of equations based on the components of each vector:

a(0,1,1)+b(1,2,2)+c(3,1,0)=(4,7,1)a(0, 1, 1) + b(1, 2, -2) + c(3, 1, 0) = (-4, 7, 1)

Breaking it down into three separate equations for each component:

  1. For the first component: 0a+1b+3c=40a + 1b + 3c = -4 b+3c=4b + 3c = -4

  2. For the second component: 1a+2b+1c=71a + 2b + 1c = 7 a+2b+c=7a + 2b + c = 7

  3. For the third component: 1a2b+0c=11a - 2b + 0c = 1 a2b=1a - 2b = 1

Solving the system of equations:

We have the following system of three equations:

  1. b+3c=4b + 3c = -4
  2. a+2b+c=7a + 2b + c = 7
  3. a2b=1a - 2b = 1

Let’s solve this step by step.

  1. Solve for bb in terms of cc from equation 1: b=43cb = -4 - 3c

  2. Substitute this expression for bb into equation 2: a+2(43c)+c=7a + 2(-4 - 3c) + c = 7 a86c+c=7a - 8 - 6c + c = 7 a85c=7a - 8 - 5c = 7 a=15+5ca = 15 + 5c

  3. Substitute this expression for aa and b=43cb = -4 - 3c into equation 3: (15+5c)2(43c)=1(15 + 5c) - 2(-4 - 3c) = 1 15+5c+8+6c=115 + 5c + 8 + 6c = 1 23+11c=123 + 11c = 1 11c=2211c = -22 c=2c = -2

  4. Substitute c=2c = -2 into the equation for bb: b=43(2)=4+6=2b = -4 - 3(-2) = -4 + 6 = 2

  5. Finally, substitute c=2c = -2 into the equation for aa: a=15+5(2)=1510=5a = 15 + 5(-2) = 15 - 10 = 5

Final Answer:

The scalars are: a=5,b=2,c=2a = 5, \quad b = 2, \quad c = -2

Thus, the vector v=(4,7,1)\mathbf{v} = (-4, 7, 1) can be written as: v=5v1+2v22v3\mathbf{v} = 5\mathbf{v_1} + 2\mathbf{v_2} - 2\mathbf{v_3}

Would you like a more detailed breakdown of any step?

Here are five related questions:

  1. How can we solve a system of linear equations using matrices?
  2. What is the geometric interpretation of expressing vectors as linear combinations?
  3. How do we know if a set of vectors forms a basis in R3\mathbb{R}^3?
  4. What is the condition for three vectors to be linearly independent in R3\mathbb{R}^3?
  5. How can linear transformations be represented using matrix operations?

Tip: When solving systems of equations, substitution works well when one variable is easy to isolate. For larger systems, consider matrix methods like Gaussian elimination.

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Math Problem Analysis

Mathematical Concepts

Linear Algebra
Vector Spaces
Linear Combinations
Systems of Equations

Formulas

v = a * v1 + b * v2 + c * v3
System of equations from vector components: a * v1 + b * v2 + c * v3 = v

Theorems

Linear Independence and Span
Basis of a Vector Space

Suitable Grade Level

University Level (Linear Algebra)