Math Problem Statement

Solve the following systems of equations by elimination, if a solution exists: 2x = 8 - 4y 5x + 5y = 12

Solution

To solve the system of equations by elimination, we proceed as follows:

Given system:

  1. 2x=84y2x = 8 - 4y
  2. 5x+5y=125x + 5y = 12

Step 1: Rewrite equations in standard form

  1. From 2x=84y2x = 8 - 4y, rearrange to:
    2x+4y=82x + 4y = 8
  2. The second equation is already in standard form:
    5x+5y=125x + 5y = 12

So, the system becomes: 2x + 4y = 8 \tag{1} 5x + 5y = 12 \tag{2}

Step 2: Eliminate one variable

To eliminate yy, we make the coefficients of yy the same by multiplying equations appropriately:

  • Multiply equation (1) by 55: 10x + 20y = 40 \tag{3}
  • Multiply equation (2) by 44: 20x + 20y = 48 \tag{4}

Now subtract equation (3) from equation (4): (20x+20y)(10x+20y)=4840(20x + 20y) - (10x + 20y) = 48 - 40 10x=810x = 8 x=810=45x = \frac{8}{10} = \frac{4}{5}

Step 3: Substitute x=45x = \frac{4}{5} into one of the original equations

Substitute into 2x+4y=82x + 4y = 8: 2(45)+4y=82\left(\frac{4}{5}\right) + 4y = 8 85+4y=8\frac{8}{5} + 4y = 8 4y=8854y = 8 - \frac{8}{5} 4y=405854y = \frac{40}{5} - \frac{8}{5} 4y=3254y = \frac{32}{5} y=325÷4=325×14y = \frac{32}{5} \div 4 = \frac{32}{5} \times \frac{1}{4} y=85y = \frac{8}{5}

Final Answer:

x=45,  y=85x = \frac{4}{5}, \; y = \frac{8}{5}

The correct choice is: A. The solution to the system is x=45,y=85x = \frac{4}{5}, y = \frac{8}{5}.

Let me know if you'd like a detailed explanation or have any questions!

Questions for deeper understanding:

  1. How does elimination compare to substitution for solving systems of equations?
  2. What happens if the system has no solution or infinitely many solutions?
  3. Can this problem be solved using matrices or graphing? How?
  4. How can you check the solution of a system of equations?
  5. What are common pitfalls when solving systems by elimination?

Tip:

Always simplify the coefficients before elimination to make calculations easier!

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Math Problem Analysis

Mathematical Concepts

Systems of Linear Equations
Elimination Method
Linear Algebra

Formulas

Standard form of a linear equation: Ax + By = C

Theorems

Properties of linear systems: consistent, inconsistent, or dependent

Suitable Grade Level

Grades 8-10