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In Exercises 5 - 12, solve the system by the method of elimination. Label each line with its equation. To print an enlarged copy of the graph \( \left\\{\begin{array}{l}9x - 3y = -15\\\\-3x + y = 5\end{array}\right. \)

Short Answer

Expert verified
The solution to the system of equations is (-5/3 , 0)

Step by step solution

01

Identify the suitable variable for elimination

We can notice that the y variable in both equations have coefficients that are negatives of each other (-3 and 1). This forms an ideal situation for adding the two equations to get rid of y.
02

Add the two equations

Simply add the two equations. Doing so will result in \(9x - 3y - 3x + y = -15 + 5\). This simplifies to \(6x = -10\).
03

Solve the resulting equation

Solving the resulting equation \(6x = -10\) gives us \(x = -\frac{10}{6}\) which simplifies to \(x = -\frac{5}{3}\).
04

Substitute the value of x in the second equation

Substitute x = -5/3 in the second equation -3x + y = 5, which simplifies to \(-3(-5/3) + y = 5\). This simplifies to \(5 + y = 5\) or \(y = 0\).
05

Check and Verify the solution

Substitute the values of x = -5/3 and y = 0 into both original equations to ensure they are satisfied.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Method of Elimination
The method of elimination is a strategy to solve systems of linear equations. This technique involves combining equations to eliminate one of the variables, making it possible to solve for the other variable. For instance, when working with the equations given in the exercise, the goal was to eliminate the variable y.

To execute the elimination, we looked for coefficients of y that were opposites or could be made opposites, such as -3 and 1 in this case. When one equation is multiplied or adjusted so that the coefficients of one variable are additive inverses, adding the equations cancels out that variable. Upon adding, you get a single-variable equation that's much simpler to solve. After finding the value for one variable, you can substitute it back into either of the original equations to find the value of the second variable. This step-by-step approach simplifies the system into a format that unveils the solution.
Systems of Linear Equations
A system of linear equations consists of two or more linear equations that have the same variables and are considered simultaneously. The solution to such a system is a set of values for each variable that satisfies all equations in the system. When graphed, each equation corresponds to a line, and the intersection of these lines represents the common solution.

In the context of the exercise provided, we are working with a system of two linear equations. The objective was to find a pair of values for x and y that fits both equations. There are several ways to solve these systems, including graphing, substitution, and elimination. The elimination method, which was demonstrated in the exercise, is ideal when the coefficients of one of the variables can be easily manipulated to cancel each other out.
Algebraic Manipulation
Algebraic manipulation is the process of rearranging and simplifying algebraic expressions and equations to solve for unknowns. This set of techniques is fundamental in solving systems of equations by elimination. When we tackle the exercise by addition, we are employing algebraic manipulation to combine equations strategically, keeping the properties of equality in mind.

Manipulation includes operations such as adding, subtracting, multiplying, or dividing both sides of an equation by the same number to maintain balance. In the exercise, we added the two equations directly because the coefficients of y were conveniently set for elimination. However, sometimes it may be necessary to multiply the entirety of one or both equations by a number to achieve coefficients that are negatives of each other for the variable we aim to eliminate. Mastery of algebraic manipulation is not just helpful; it's crucial for efficiently and accurately solving systems of equations.

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Most popular questions from this chapter

In Exercises 41-54, sketch the graph and label the vertices of the solution set of the system of inequalities. \( \left\\{\begin{array}{l} x^2 + y^2 \le 25\\\ 4x - 3y \le 0\end{array}\right. \)

A manufacturer produces two models of elliptical cross-training exercise machines. The times for assembling, finishing, and packaging model \( X \) are 3 hours, 3 hours, and 0.8 hour, respectively. The times for model \( Y \) are 4 hours, 2.5 hours, and 0.4 hour. The total times available for assembling, finishing, and packaging are 6000 hours, 4200 hours, and 950 hours, respectively. The profits per unit are \( \$300 \) for model \( X \) and \( \$375 \) for model \( Y \). What is the optimal production level for each model? What is the optimal profit?

A merchant plans to sell two models of MP3 players at prices of \(\$ 225\) and \(\$ 250\) . The \(\$ 225\) model yields a profit of \(\$ 30\) per unit and the \(\$ 250\) model yields a profit of \(\$ 31\) per unit. The merchant estimates that the total monthly demand will not exceed 275 units. The merchant does not want to invest more than \(\$ 63,000\) in inventory for these products. What is the optimal inventory level for each model? What is the optimal profit?

In Exercises 55-60, use a graphing utility to graph the solution set of the system of inequalities. \( \left\\{\begin{array}{l} y < -x^2 + 2x + 3\\\ y > x^2 - 4x + 3\end{array}\right. \)

A dietitian is asked to design a special dietary supplement using two different foods. Each ounce of food \( X \) contains 20 units of calcium, 15 units of iron, and 10 units of vitamin \( B \). Each ounce of food \( Y \) contains 10 units of calcium, 10 units of iron, and 20 units of vitamin \( B \). The minimum daily requirements of the diet are 300 units of calcium, 150 units of iron, and 200 units of vitamin \( B \). (a) Write a system of inequalities describing the different amounts of food \( X \) and food \( Y \) that can be used. (b) Sketch a graph of the region corresponding to the system in part (a). (c) Find two solutions of the system and interpret their meanings in the context of the problem.

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