Math Problem Statement

Which strategy can you use to eliminate a variable in the system of equations: 5x + 3y = 4 and -2x - 8y = 6?

Solution

The question presents a system of linear equations:

  1. 5x+3y=45x + 3y = 4
  2. 2x8y=6-2x - 8y = 6

It asks which strategy can be used to eliminate a variable by applying a multiplier to one or both equations and then adding the equations.

Step 1: Analyze the system of equations

To eliminate a variable, we can make the coefficients of either xx or yy the same in both equations and then add them.

Eliminating xx:

  • The coefficients of xx are 55 and 2-2. To make them the same, we find their least common multiple (LCM), which is 10.
    • Multiply the first equation by 2: (5x+3y=4)×210x+6y=8(5x + 3y = 4) \times 2 \rightarrow 10x + 6y = 8
    • Multiply the second equation by 5: (2x8y=6)×510x40y=30(-2x - 8y = 6) \times 5 \rightarrow -10x - 40y = 30

Adding these equations will eliminate xx.

Eliminating yy:

  • The coefficients of yy are 33 and 8-8. Their LCM is 24.
    • Multiply the first equation by 8: (5x+3y=4)×840x+24y=32(5x + 3y = 4) \times 8 \rightarrow 40x + 24y = 32
    • Multiply the second equation by 3: (2x8y=6)×36x24y=18(-2x - 8y = 6) \times 3 \rightarrow -6x - 24y = 18

Adding these equations will eliminate yy.

Matching to the options:

The correct answer matches "Multiply the first equation by 2 and the second equation by 5. Then add the equations." This strategy eliminates xx.

Let me know if you'd like further clarification or step-by-step solving of the system!


Questions to Expand:

  1. What happens when you eliminate yy instead of xx?
  2. How would substitution work for solving this system instead of elimination?
  3. Why do we multiply equations to align coefficients for elimination?
  4. Can this system be solved graphically, and what does the solution represent?
  5. What is the significance of the LCM when choosing multipliers for elimination?

Tip:

When using elimination, always align the coefficients carefully to avoid errors, and double-check the addition step!

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Math Problem Analysis

Mathematical Concepts

Algebra
Systems of Linear Equations
Elimination Method

Formulas

Equation for elimination: ax + by = c

Theorems

Elimination method for solving systems of equations

Suitable Grade Level

Grade 8