Math Problem Statement

Use the method of elimination to solve the following system of equations. If the system is dependent, express the solution set in terms of one of the variables. Leave all fractional answers in fraction form. The system of equations is: 2x + 5y = 18 8x + 20y = 72

Solution

The system of equations provided is:

2x + 5y &= 18 \\ 8x + 20y &= 72 \end{aligned}$$ We will use the **method of elimination** to solve the system. ### Step 1: Simplify the second equation (if possible) Notice that the second equation can be simplified. Divide the entire second equation by 4: $$\frac{8x + 20y}{4} = \frac{72}{4} \implies 2x + 5y = 18$$ Thus, both equations are actually the same: $$2x + 5y = 18$$ ### Step 2: Determine the type of system Since the two equations are identical, we have a **dependent system**, meaning there are infinitely many solutions. The solution set will depend on one of the variables. ### Step 3: Express the solution Since the system is dependent, we can express one variable in terms of the other. Using the first equation $$2x + 5y = 18$$, solve for $$x$$ in terms of $$y$$: $$x = \frac{18 - 5y}{2}$$ Thus, the general solution is: $$(x, y) = \left( \frac{18 - 5y}{2}, y \right)$$ ### Conclusion: The system is **dependent**, and the solution set is $$\left( \frac{18 - 5y}{2}, y \right)$$, where $$y$$ is any real number. Would you like more details on this method or how to handle such systems? Here are some related questions: 1. How can you tell if a system of equations is dependent? 2. What are the key differences between dependent and inconsistent systems? 3. How do you approach solving systems using substitution versus elimination? 4. In what scenarios would a system have only one solution? 5. What is the geometric interpretation of a dependent system of linear equations? **Tip:** Always check if equations can be simplified before applying elimination to save time.

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Math Problem Analysis

Mathematical Concepts

Algebra
Linear Systems
Elimination Method
Dependent Systems

Formulas

Elimination method for solving systems
Linear equation: ax + by = c

Theorems

The solution of dependent systems in linear equations

Suitable Grade Level

Grades 9-12