Ch. 5 - Systems of Equations and Inequalities

Blitzer8th EditionCollege AlgebraISBN: 9780136970514Not the one you use?Change textbook

Blitzer 8th Edition

Ch. 5 - Systems of Equations and Inequalities

Problem 49

Chapter 6, Problem 49

In Exercises 49–50, solve each system for x and y, expressing either value in terms of a or b, if necessary. Assume that a ≠ 0, b ≠ 0 5ax + 4y = 17 ax + 7y = 22

Verified step by step guidance

Start with the system of equations:

5ax + 4y = 17 ax + 7y = 22

To solve for

x

and

y

, use the method of elimination or substitution. Here, elimination is convenient. Multiply the second equation by 5 to align the coefficients of

ax

5(ax) + 5(7y) = 5(22) which simplifies to 5ax + 35y = 110 .

Now subtract the first equation from this new equation to eliminate

5ax

(5ax + 35y) - (5ax + 4y) = 110 - 17 which simplifies to 31y = 93 .

Solve for

y

by dividing both sides by 31:

y = \(\frac{93}{31}\)

. Since the problem asks to express in terms of

a

b

if necessary, check if any variables remain; here,

y

is a constant.

Substitute the value of

y

back into one of the original equations, for example,

ax + 7y = 22

, to solve for

x

. Rearrange to isolate

x

ax = 22 - 7y

, then

x = \(\frac{22 - 7y}{a}\)

. This expresses

x

in terms of

a

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Solving Systems of Linear Equations

A system of linear equations consists of two or more linear equations with the same variables. The goal is to find values for the variables that satisfy all equations simultaneously. Common methods include substitution, elimination, and using matrices. In this problem, solving for x and y involves manipulating the equations to isolate one variable and substitute it into the other.

Expressing Variables in Terms of Parameters

When equations contain parameters like a and b, solutions for variables x and y may be expressed in terms of these parameters. This means the solution is not a single number but a formula depending on a and b. It is important to treat parameters as constants during algebraic manipulation, ensuring conditions like a ≠ 0 are considered to avoid division by zero.

Elimination Method for Systems with Parameters

The elimination method involves adding or subtracting equations to eliminate one variable, making it easier to solve for the other. When parameters are involved, coefficients include variables like a, so careful algebraic manipulation is needed. After eliminating one variable, the remaining equation can be solved for the other variable in terms of the parameters.

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Solving Systems of Equations - Elimination

Related Practice

Textbook Question

In Exercises 47–52, solve each system by the method of your choice. $\begin{cases}\)2x^2 + xy = 6 $\x$^2 + 2xy = 0\(\end{cases}$

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Textbook Question

In Exercises 47–52, solve each system by the method of your choice. $\begin{cases}\]\frac{3}{x^2}\) + $\frac{1}{y^2}$ = 7 $\frac{5}{x^2}$ - $\frac{2}{y^2}$ = -3\(\end{cases}$

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Textbook Question

Find the partial fraction decomposition for 1/x(x+1) and use the result to find the following sum:

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Textbook Question

In Exercises 47–48, solve each system by the method of your choice. (x - y)/3 = (x + y)/2 - 1/2 (x + 2)/2 - 4 = (y + 4)/3

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Textbook Question

In Exercises 47–52, solve each system by the method of your choice. $\begin{cases}\)-4x + y = 12 $\y$ = x^3 + 3x^2\(\end{cases}$

Textbook Question

Graph the solution set of each system of inequalities or indicate that the system has no solution.

$\begin{cases}\)x^2 + y^2 > 1 $\x$^2 + y^2 < 16\(\end{cases}$