Back to College Algebra

11.1 Systems of Linear Equations: Two Variables

Graphing, substitution, and addition applied to two-equation systems, plus spotting inconsistent and dependent cases.

Algebra and Trigonometry 2e, 11.1 Systems of Linear Equations: Two Variables

Status
FlagsLoading your progress…

55 exercises

11.1 Exercise 1

Determine whether the ordered pairs are solutions to the given system.

2x-6y=03x-y=5\left\{\begin{matrix} 2 x - 6 y = 0 \\ 3 x - y = 5 \end{matrix}\right at (3, 1)\left(3 , 1\right) and (-3, 4)\left(- 3 , 4\right)

2.5

Determining Whether an Ordered Pair Is a Solution to a System of Equations

Determine whether the ordered pair ( 5,1 ) \left(5 , 1\right) is a solution to the given system of equations.

2.5

11.1 Exercise 8

Determine whether the ordered pair ( 8,5 ) \left(8 , 5\right) is a solution to the following system.

5x−4y=20 2x+1=3y \begin{matrix}5 x −4 y = 20 \\ 2 x + 1 = 3 y\end{matrix}
2.5

Solving a System of Equations in Two Variables by Substitution

Solve the following system of equations by substitution.

2.5

11.1 Exercise 12

Solve the following system of equations by substitution.

2.5

Solving a System by the Addition Method

Solve the given system of equations by addition.

2.5

11.1 Exercise 15

Solve the system of equations by addition.

2x−7y=2 3x+y=−20 \begin{matrix}2 x −7 y = 2 \\ 3 x + y = −20\end{matrix}
2.5

Using the Addition Method in Systems of Equations Containing Fractions

Solve the given system of equations in two variables by addition.

2.5

11.1 Exercise 18

Solve the system of equations by addition.

2x+3y=83x+5y=10\begin{aligned}2 x + 3 y & = & 8 \\ 3 x + 5 y & = & 10\end{aligned}
2.5

Solving an Inconsistent System of Equations

Solve the following system of equations.

2.5

11.1 Exercise 20

Solve the following system of equations in two variables.

2.5

Finding a Solution to a Dependent System of Linear Equations

Find a solution to the system of equations using the addition method.

2.5

11.1 Exercise 22

Solve the following system of equations in two variables.

2.5

Finding the Break-Even Point and the Profit Function Using Substitution

Given the cost function C(x)=0.85x+35,000 C \left(x\right) = 0.85 x + 35,000 and the revenue function R(x)=1.55x, R \left(x\right) = 1.55 x , find the break-even point and the profit function.

2.5

Writing and Solving a System of Equations in Two Variables

The cost of a ticket to the circus is $25.00 \$ 25.00 for children and $50.00 \$ 50.00 for adults. On a certain day, attendance at the circus is 2,000 2,000 and the total gate revenue is $70,000. \$ 70,000. How many children and how many adults bought tickets?

2.5

11.1 Exercise 25

Meal tickets at the circus cost $4.00 \$ 4.00 for children and $12.00 \$ 12.00 for adults. If 1,650 1,650 meal tickets were bought for a total of $14,200, \$ 14,200 , how many children and how many adults bought meal tickets?

2.5

11.1 Exercise 26

Can a system of linear equations have exactly two solutions? Explain why or why not.

2.5

11.1 Exercise 28

If you are solving a break-even analysis and get a negative break-even point, explain what this signifies for the company?

2.5

11.1 Exercise 30

Given a system of equations, explain at least two different methods of solving that system.

2.5

11.1 Exercise 32

Determine whether the given ordered pair is a solution to the system of equations.

−3x−5y=13 −x+4y=10 \begin{matrix}−3 x - 5 y = 13 \\ - x + 4 y = 10\end{matrix} and (−6,1) \left(−6 , 1\right)

2.5

11.1 Exercise 34

Determine whether the given ordered pair is a solution to the system of equations.

−2x+5y=7 2x+9y=7 \begin{matrix}−2 x + 5 y = 7 \\ 2 x + 9 y = 7\end{matrix} and (−1,1) \left(−1 , 1\right)

2.5

11.1 Exercise 36

Solve each system by substitution.

x+3y=5 2x+3y=4 \begin{matrix} x + 3 y = 5 \\ 2 x + 3 y = 4\end{matrix}

2.5

11.1 Exercise 38

Solve each system by substitution.

4x+2y=−10 3x+9y=0 \begin{matrix}4 x + 2 y = −10 \\ 3 x + 9 y = 0\end{matrix}

2.5

11.1 Exercise 40

Solve each system by substitution.

−2x+3y=1.2 −3x−6y=1.8 \begin{matrix}- 2 x + 3 y = 1.2 \\ - 3 x - 6 y = 1.8\end{matrix}

2.5

11.1 Exercise 42

Solve each system by substitution.

3x+5y=9 30x+50y=−90 \begin{matrix} \text{ } 3 x + 5 y = 9 \\ 30 x + 50 y = −90\end{matrix}

2.5

11.1 Exercise 44

Solve each system by substitution.

1 2 x+ 1 3 y=16 1 6 x+ 1 4 y=9 \begin{matrix}\frac{1}{2} x + \frac{1}{3} y = 16 \\ \frac{1}{6} x + \frac{1}{4} y = 9\end{matrix}

2.5

11.1 Exercise 46

Solve each system by addition.

−2x+5y=−42 7x+2y=30 \begin{matrix}−2 x + 5 y = −42 \\ 7 x + 2 y = 30\end{matrix}

2.5

11.1 Exercise 48

Solve each system by addition.

5x−y=−2.6 −4x−6y=1.4 \begin{matrix} \text{ } 5 x - y = −2.6 \\ −4 x −6 y = 1.4\end{matrix}

2.5

11.1 Exercise 50

Solve each system by addition.

−x+2y=−1 5x−10y=6 \begin{matrix} −x + 2 y = −1 \\ 5 x −10 y = 6\end{matrix}

2.5

11.1 Exercise 52

Solve each system by addition.

5 6 x+ 1 4 y=0 1 8 x− 1 2 y=− 43 120 \begin{matrix}\frac{5}{6} x + \frac{1}{4} y = 0 \\ \frac{1}{8} x - \frac{1}{2} y = - \frac{43}{120}\end{matrix}

2.5

11.1 Exercise 54

Solve each system by addition.

−0.2x+0.4y=0.6 x−2y=−3 \begin{matrix} \\ \begin{matrix}−0.2 x + 0.4 y = 0.6 \\ \text{ } x −2 y = −3\end{matrix}\end{matrix}

2.5

11.1 Exercise 56

Solve each system by any method.

5x+9y=16 x+2y=4 \begin{matrix}5 x + 9 y = 16 \\ \text{ } x + 2 y = 4\end{matrix}

2.5

11.1 Exercise 58

Solve each system by any method.

5x−2y=2.25 7x−4y=3 \begin{matrix}5 x −2 y = 2.25 \\ 7 x −4 y = 3\end{matrix}

2.5

11.1 Exercise 60

Solve each system by any method.

7x−4y= 7 6 2x+4y= 1 3 \begin{matrix}7 x −4 y = \frac{7}{6} \\ 2 x + 4 y = \frac{1}{3}\end{matrix}

2.5

11.1 Exercise 62

Solve each system by any method.

7 3 x− 1 6 y=2 − 21 6 x+ 3 12 y=−3 \begin{matrix} \text{ } \frac{7}{3} x - \frac{1}{6} y = 2 \\ - \frac{21}{6} x + \frac{3}{12} y = −3\end{matrix}

2.5

11.1 Exercise 64

Solve each system by any method.

2.2x+1.3y=−0.1 4.2x+4.2y=2.1 \begin{matrix}2.2 x + 1.3 y = −0.1 \\ 4.2 x + 4.2 y = 2.1\end{matrix}

2.5

11.1 Exercise 66

Graph the system of equations and state whether the system is consistent, inconsistent, or dependent and whether the system has one solution, no solution, or infinite solutions.

3x−y=0.6 x−2y=1.3 \begin{matrix}3 x - y = 0.6 \\ x −2 y = 1.3\end{matrix}

2.5

11.1 Exercise 68

Graph the system of equations and state whether the system is consistent, inconsistent, or dependent and whether the system has one solution, no solution, or infinite solutions.

x+2y=7 2x+6y=12 \begin{matrix} x + 2 y = 7 \\ 2 x + 6 y = 12\end{matrix}

2.5

11.1 Exercise 70

Graph the system of equations and state whether the system is consistent, inconsistent, or dependent and whether the system has one solution, no solution, or infinite solutions.

3x−2y=5 −9x+6y=−15 \begin{matrix} 3 x −2 y = 5 \\ −9 x + 6 y = −15\end{matrix}

2.5

11.1 Exercise 72

Use the intersect function on a graphing device to solve each system. Round all answers to the nearest hundredth.

−0.01x+0.12y=0.62 0.15x+0.20y=0.52 \begin{matrix}−0.01 x + 0.12 y = 0.62 \\ 0.15 x + 0.20 y = 0.52\end{matrix}

2.5

11.1 Exercise 74

Use the intersect function on a graphing device to solve each system. Round all answers to the nearest hundredth.

0.15x+0.27y=0.39 −0.34x+0.56y=1.8 \begin{matrix} 0.15 x + 0.27 y = 0.39 \\ −0.34 x + 0.56 y = 1.8\end{matrix}

2.5

11.1 Exercise 76

Solve each system in terms of A,B,C,D,E, A , B , C , D , E , and F F where A–F A – F are nonzero numbers. Note that A≠B A \neq B and AE≠BD. A E \neq B D .

x+y=A x−y=B \begin{matrix}x + y = A \\ x - y = B\end{matrix}

2.5

11.1 Exercise 78

Solve each system in terms of A,B,C,D,E, A , B , C , D , E , and F F where A–F A – F are nonzero numbers. Note that A≠B A \neq B and AE≠BD. A E \neq B D .

Ax+y=0 Bx+y=1 \begin{matrix}A x + y = 0 \\ B x + y = 1\end{matrix}

2.5

11.1 Exercise 80

Solve each system in terms of A,B,C,D,E, A , B , C , D , E , and F F where A–F A – F are nonzero numbers. Note that A≠B A \neq B and AE≠BD. A E \neq B D .

Ax+By=C Dx+Ey=F \begin{matrix}A x + B y = C \\ D x + E y = F\end{matrix}

2.5

11.1 Exercise 82

Solve for the desired quantity.

An Ethiopian restaurant has a cost of production C(x)=11x+120 C \left(x\right) = 11 x + 120 and a revenue function R(x)=5x. R \left(x\right) = 5 x . When does the company start to turn a profit?

2.5

11.1 Exercise 84

Solve for the desired quantity.

A musician charges C(x)=64x+20,000 C \left(x\right) = 64 x + 20,000 where x x is the total number of attendees at the concert. The venue charges $80 per ticket. After how many people buy tickets does the venue break even, and what is the value of the total tickets sold at that point?

2.5

11.1 Exercise 86

Use a system of linear equations with two variables and two equations to solve.

Find two numbers whose sum is 28 and difference is 13.

2.5

11.1 Exercise 88

Use a system of linear equations with two variables and two equations to solve.

The startup cost for a restaurant is $120,000, and each meal costs $10 for the restaurant to make. If each meal is then sold for $15, after how many meals does the restaurant break even?

2.5

11.1 Exercise 90

Use a system of linear equations with two variables and two equations to solve.

A total of 1,595 first- and second-year college students gathered at a pep rally. The number of first-years exceeded the number of second-years by 15. How many students from each year group were in attendance?

2.5

11.1 Exercise 92

Use a system of linear equations with two variables and two equations to solve.

There were 130 faculty at a conference. If there were 18 more women than men attending, how many of each gender attended the conference?

2.5

11.1 Exercise 94

Use a system of linear equations with two variables and two equations to solve.

If a scientist mixed 10% saline solution with 60% saline solution to get 25 gallons of 40% saline solution, how many gallons of 10% and 60% solutions were mixed?

2.5

11.1 Exercise 96

Use a system of linear equations with two variables and two equations to solve.

An investor invested 1.1 million dollars into two land investments. On the first investment, Swan Peak, her return was a 110% increase on the money she invested. On the second investment, Riverside Community, she earned 50% over what she invested. If she earned $1 million in profits, how much did she invest in each of t…

2.5

11.1 Exercise 98

Use a system of linear equations with two variables and two equations to solve.

If an investor invests $23,000 into two bonds, one that pays 4% in simple interest, and the other paying 2% simple interest, and the investor earns $710.00 annual interest, how much was invested in each account?

2.5

11.1 Exercise 100

Use a system of linear equations with two variables and two equations to solve.

A store clerk sold 60 pairs of sneakers. The high-tops sold for $98.99 and the low-tops sold for $129.99. If the receipts for the two types of sales totaled $6,404.40, how many of each type of sneaker were sold?

2.5

11.1 Exercise 102

Use a system of linear equations with two variables and two equations to solve.

Admission into an amusement park for 4 children and 2 adults is $116.90. For 6 children and 3 adults, the admission is $175.35. Assuming a different price for children and adults, what is the price of the child’s ticket and the price of the adult ticket?

2.5

Adapted from College Algebra © 2021 Rice University. Licensed under CC BY 4.0. Sources: College Algebra 2e, Algebra and Trigonometry 2e, Precalculus 2e, College Algebra with Corequisite Support 2e. Imported at revision 4922e46.