Math Problem Statement

Determine if b is in the span of the other given vectors. If so, express b as a linear combination of the other vectors. (If b cannot be written as a linear combination of the other two vectors, enter DNE in both answer blanks.) a1 =

−1

3 −1 , a2 =

−2

−3 6 , b =

−5

6 3

Solution

To determine whether the vector b\mathbf{b} can be written as a linear combination of vectors a1\mathbf{a}_1 and a2\mathbf{a}_2, we need to solve the equation:

c1a1+c2a2=bc_1 \mathbf{a}_1 + c_2 \mathbf{a}_2 = \mathbf{b}

Where: a1=(131),a2=(236),b=(563)\mathbf{a}_1 = \begin{pmatrix} -1 \\ 3 \\ -1 \end{pmatrix}, \quad \mathbf{a}_2 = \begin{pmatrix} -2 \\ -3 \\ 6 \end{pmatrix}, \quad \mathbf{b} = \begin{pmatrix} -5 \\ 6 \\ 3 \end{pmatrix}

This gives the following system of equations:

c1(1)+c2(2)=5c_1(-1) + c_2(-2) = -5 c1(3)+c2(3)=6c_1(3) + c_2(-3) = 6 c1(1)+c2(6)=3c_1(-1) + c_2(6) = 3

We now solve this system to determine if c1c_1 and c2c_2 exist.

Equation 1:

c12c2=5-c_1 - 2c_2 = -5

This simplifies to: c1+2c2=5(Eq 1)c_1 + 2c_2 = 5 \quad \text{(Eq 1)}

Equation 2:

3c13c2=63c_1 - 3c_2 = 6

Dividing the entire equation by 3: c1c2=2(Eq 2)c_1 - c_2 = 2 \quad \text{(Eq 2)}

Equation 3:

c1+6c2=3-c_1 + 6c_2 = 3

This simplifies to: c16c2=3(Eq 3)c_1 - 6c_2 = -3 \quad \text{(Eq 3)}

Now, we can solve these equations step by step.

From Eq 2, we have c1=c2+2c_1 = c_2 + 2.

Substitute c1=c2+2c_1 = c_2 + 2 into Eq 1: (c2+2)+2c2=5(c_2 + 2) + 2c_2 = 5 c2+2+2c2=5c_2 + 2 + 2c_2 = 5 3c2+2=53c_2 + 2 = 5 3c2=33c_2 = 3 c2=1c_2 = 1

Now, substitute c2=1c_2 = 1 back into Eq 2: c11=2c_1 - 1 = 2 c1=3c_1 = 3

Check Solution with Eq 3:

Substitute c1=3c_1 = 3 and c2=1c_2 = 1 into Eq 3: 36(1)=33 - 6(1) = -3 36=33 - 6 = -3 This is true, so the solution is valid.

Thus, b\mathbf{b} can be written as a linear combination of a1\mathbf{a}_1 and a2\mathbf{a}_2: b=3a1+1a2\mathbf{b} = 3\mathbf{a}_1 + 1\mathbf{a}_2

Final Answer:

c1=3,c2=1c_1 = 3, \quad c_2 = 1

Do you need more details or have any questions?

Here are 5 relative questions to expand on this concept:

  1. What is the geometric interpretation of linear combinations and vector spans?
  2. How can you determine if three vectors are linearly dependent or independent?
  3. What does it mean for a vector to be in the span of other vectors?
  4. How does the row-reduction method help in solving systems of linear equations like this?
  5. Can the cross product be used to find relationships between vectors in 3D space?

Tip: Always check your solution by substituting the found coefficients back into the original equations to ensure consistency.

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Math Problem Analysis

Mathematical Concepts

Linear Algebra
Vector Spaces
Linear Combinations
Systems of Equations

Formulas

c1 * a1 + c2 * a2 = b
Solving system of linear equations via substitution

Theorems

Linear Combination Theorem
Span of Vectors

Suitable Grade Level

Undergraduate Level (College Algebra, Linear Algebra)