4.2 Solve Applications with Systems of Equations

3 min readโ€ขjune 24, 2024

are powerful tools for solving real-world problems. They allow us to translate complex scenarios into mathematical models, using variables to represent unknowns and equations to capture relationships between quantities.

From geometry to motion analysis, systems of equations help us find optimal solutions. By setting up and solving these systems, we can tackle a wide range of practical applications, making algebra a versatile problem-solving tool in many fields.

Solving Applications with Systems of Equations

Translation of word problems

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  • Identify the unknown variables in the problem
    • Assign a variable to each unknown quantity (xx for the first unknown, yy for the second unknown)
    • Determine which are dependent and
  • Write equations based on the given information
    • Express the relationships between variables using the problem's context
    • Represent each piece of information with an equation
  • Solve the resulting system of equations
    • Find the values of the unknown variables using substitution, elimination, or graphing methods
  • Interpret the solution in the context of the original problem
    • Check if the solution makes sense and answers the question asked

Systems of equations for geometry

  • Identify the geometric shapes and measurements involved
    • Recognize relationships between shapes and their dimensions (length, width, area)
  • Assign variables to the unknown measurements
    • Use variables to represent relevant quantities (side lengths, perimeter)
  • Create equations based on geometric properties and given information
    • Use formulas for area, perimeter, or other geometric relationships to set up equations
    • Express relationships between shapes and dimensions using assigned variables
  • Solve the resulting system of equations
    • Find values of unknown measurements using substitution, elimination, or graphing
  • Interpret the solution in the context of the geometric problem
    • Verify the solution satisfies given conditions and makes sense for the shapes

Uniform motion analysis

  • Identify moving objects and their characteristics
    • Recognize initial positions, velocities, and directions of motion for each object
  • Assign variables to unknown quantities
    • Use variables to represent distances traveled, times, or other relevant quantities
  • Create equations based on formulas and given information
    • Use d=vtd = vt (distance = velocity ร— time) to set up equations for each moving object
    • Express relationships between objects' positions and times using assigned variables
  • Solve the resulting system of equations
    • Find values of unknown quantities using substitution, elimination, or graphing
  • Interpret the solution in the context of the motion scenario
    • Determine positions of objects at specific times or when certain conditions are met
    • Verify the solution makes sense in the context of the motion problem

Algebraic Modeling and Optimization

  • Develop algebraic models to represent real-world scenarios
    • Use variables and equations to describe relationships in the problem
    • Identify that limit possible solutions
  • Formulate problems using systems of equations
    • Define an objective function to maximize or minimize
    • Determine the feasible region based on constraints
  • Solve the system to find optimal solutions
    • Use algebraic or graphical methods to identify the best solution within constraints

Key Terms to Review (25)

Addition Principle: The addition principle is a fundamental concept in solving systems of equations. It states that when two or more equations are added together, the resulting equation will also be a valid solution to the original system of equations.
Algebraic Modeling: Algebraic modeling is the process of representing real-world situations and problems using mathematical equations and expressions. It involves translating verbal descriptions, relationships, and constraints into an algebraic framework that can be used to analyze, solve, and make predictions about the problem at hand.
Back-Substitution: Back-substitution is a method used to solve systems of equations by first finding the value of one variable, then substituting that value into the other equations to find the values of the remaining variables. This technique is particularly useful in solving systems of equations with three or more variables.
Break-Even Point: The break-even point is the point at which the total revenue generated by a business or activity equals the total costs associated with that business or activity. At this point, there is no profit or loss, as the revenue exactly covers the expenses incurred.
Constraint Equations: Constraint equations are mathematical equations that represent the limitations or restrictions in a system. They are an essential component in solving applications with systems of equations, as they define the boundaries and conditions that the solution must satisfy.
Dependent Variables: Dependent variables are the variables in a system or equation that depend on and are influenced by the other variables, known as independent variables. They represent the outcomes or responses that are measured or observed in a study or experiment.
Elimination Method: The elimination method, also known as the method of elimination, is a technique used to solve systems of linear equations by systematically eliminating variables to find the unique solution. This method involves manipulating the equations in the system to isolate one variable at a time, ultimately leading to the determination of the values for all the variables in the system.
Geometric Applications: Geometric applications refer to the use of geometric concepts, principles, and techniques to solve real-world problems. These applications involve the practical implementation of geometric ideas in various fields, such as engineering, architecture, and design.
Independent Variables: An independent variable is a variable that is manipulated or changed in an experiment or study to observe its effect on the dependent variable. It is the variable that the researcher has control over and intentionally varies to measure its impact on the outcome.
Infinite Solutions: Infinite solutions refers to a situation where a linear equation or a system of linear equations has an unlimited number of solutions. This concept is particularly relevant in the context of solving linear equations, solving applications with systems of equations, and graphing systems of linear inequalities.
Intersection Point: The intersection point is the location where two or more lines, curves, or surfaces meet and cross each other. It is a critical concept in the context of solving applications with systems of equations, as it represents the unique solution where the equations intersect.
Linear Equations: A linear equation is a mathematical equation in which the variables are raised to the first power and the equation can be represented as a straight line on a graph. These equations are fundamental in solving systems of equations and graphing systems of linear inequalities.
Mixture Problems: Mixture problems are a type of application problem in mathematics that involve combining two or more substances or solutions with different properties, such as concentrations or compositions, to create a new mixture with a desired characteristic. These problems often require the use of systems of equations to solve for unknown quantities.
Multiplication Principle: The multiplication principle is a fundamental concept in mathematics that describes the relationship between the number of options or outcomes in a series of independent events. It states that if there are m possible outcomes for one event and n possible outcomes for another independent event, then the total number of possible outcomes for the combined events is the product of m and n.
No Solution: The term 'no solution' refers to a situation in which an equation, system of equations, or system of linear inequalities does not have a valid solution that satisfies all the given constraints. This means that there are no values for the variables that can make the equation or system of equations/inequalities true.
Optimization: Optimization is the process of finding the best or most favorable solution to a problem, given certain constraints or objectives. It involves selecting the optimal values for decision variables to achieve the desired outcome, whether that is maximizing a benefit or minimizing a cost.
Ordered Pair: An ordered pair is a set of two numbers or coordinates that represent a specific point on a coordinate plane. The ordered pair is typically denoted as (x, y), where x represents the horizontal position and y represents the vertical position of the point.
Rate Problems: Rate problems involve the calculation of a specific quantity over time, such as speed, flow, or production. These types of problems often require the use of systems of equations to solve for unknown variables and determine the relationships between different rates.
Simultaneous Equations: Simultaneous equations are a set of two or more equations that share common variables and must be solved together to find the values of those variables. These equations represent multiple relationships or constraints that need to be satisfied simultaneously.
Solution Set: The solution set is the set of all values of the variable(s) that satisfy an equation, inequality, or system of equations or inequalities. It represents the collection of all possible solutions to a given mathematical problem.
Substitution Method: The substitution method is a technique used to solve systems of linear equations by isolating one variable in one of the equations and then substituting that expression into the other equation(s) to solve for the remaining variable(s). This method is applicable in various contexts, including solving systems of linear equations with two variables, applications with systems of equations, mixture problems with systems of equations, systems of equations with three variables, solving radical equations, and solving systems of nonlinear equations.
Systems of Equations: A system of equations is a set of two or more equations that share common variables and must be solved simultaneously to find the values of those variables. These equations represent real-world relationships and situations that can be modeled mathematically.
Uniform Motion: Uniform motion is a type of motion where an object travels at a constant speed, maintaining the same velocity throughout its movement. This concept is fundamental in understanding various applications, including mixture problems, systems of equations, rational equations, and quadratic equations.
Unique Solution: A unique solution refers to a single, specific answer that satisfies the given system of equations or linear equation. It is the only solution that makes all the equations in the system true simultaneously.
Work Problems: Work problems are mathematical word problems that involve the calculation of work done, time taken, or the rate of work. These problems often arise in the context of various applications, including mixture problems and uniform motion problems, as well as in the solving of systems of equations.
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