Math Problem Statement

Write x as a linear combination of a and b.

Solution

To solve this problem, we need to express the green vector x\mathbf{x} as a linear combination of the two blue vectors a\mathbf{a} and b\mathbf{b}. The equation would take the form:

x=c1a+c2b\mathbf{x} = c_1 \mathbf{a} + c_2 \mathbf{b}

Where c1c_1 and c2c_2 are scalars (coefficients) for the vectors a\mathbf{a} and b\mathbf{b} respectively.

Step-by-Step Approach:

  1. Identify the vectors:

    • Vector a\mathbf{a} appears to point in the positive x-direction (right), and its coordinates are approximately a=(3,0)\mathbf{a} = (3, 0).
    • Vector b\mathbf{b} points downward and to the left, with coordinates b=(1,2)\mathbf{b} = (-1, -2).
  2. Coordinates of x\mathbf{x}:

    • The green vector x\mathbf{x} appears to point upward to the left, approximately at x=(1,4)\mathbf{x} = (-1, 4).
  3. Set up the linear combination: We need to solve for c1c_1 and c2c_2 in the following system: c1a+c2b=xc_1 \mathbf{a} + c_2 \mathbf{b} = \mathbf{x} Substituting the values for the vectors: c1(3,0)+c2(1,2)=(1,4)c_1 (3, 0) + c_2 (-1, -2) = (-1, 4)

  4. Break it into components:

    • For the x-component: 3c1c2=13c_1 - c_2 = -1
    • For the y-component: 2c2=4-2c_2 = 4
  5. Solve for c2c_2: From the second equation: 2c2=4c2=2-2c_2 = 4 \quad \Rightarrow \quad c_2 = -2

  6. Solve for c1c_1: Substitute c2=2c_2 = -2 into the first equation: 3c1(2)=13c1+2=13c_1 - (-2) = -1 \quad \Rightarrow \quad 3c_1 + 2 = -1 3c1=3c1=13c_1 = -3 \quad \Rightarrow \quad c_1 = -1

Final Answer:

The vector x\mathbf{x} can be written as: x=1a+(2)b\mathbf{x} = -1 \cdot \mathbf{a} + (-2) \cdot \mathbf{b} Or: x=a2b\mathbf{x} = -\mathbf{a} - 2\mathbf{b}

Would you like more details or have any questions?

Here are 5 related questions:

  1. How do you verify a linear combination of vectors?
  2. What is the geometric meaning of a linear combination of two vectors?
  3. How can we express a vector in different bases?
  4. How would you represent three vectors in 3D space as a linear combination?
  5. What are the conditions for vectors to form a linear basis?

Tip: When working with linear combinations, always ensure the vectors are linearly independent (i.e., they don’t lie on the same line) to guarantee that the system has a unique solution.

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Math Problem Analysis

Mathematical Concepts

Linear Combinations
Vector Algebra

Formulas

x = c1 * a + c2 * b
c1 * (3, 0) + c2 * (-1, -2) = (-1, 4)

Theorems

System of Linear Equations
Vector Decomposition

Suitable Grade Level

Grades 10-12