Solve the system of equations by graphing: - Sy=−2x – 1 (2x + 4y = 8 6

Algebra and Trigonometry (6th Edition)
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ChapterP: Prerequisites: Fundamental Concepts Of Algebra
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### Solving Systems of Equations by Graphing

#### Problem:
Solve the system of equations by graphing:

\[
\begin{cases}
y = -2x - 1 \\
2x + 4y = 8
\end{cases}
\]

#### Solution:
1. **Graph the First Equation**: \(y = -2x - 1\)

   - This is a linear equation in slope-intercept form \(y = mx + b\), where \(m\) is the slope and \(b\) is the y-intercept.
   - The y-intercept \(b = -1\), which means the line crosses the y-axis at \((0, -1)\).
   - The slope \(m = -2\) indicates that for every 1 unit increase in \(x\), \(y\) decreases by 2 units.

2. **Graph the Second Equation**: \(2x + 4y = 8\)

   - First, simplify this equation to the slope-intercept form \(y = mx + b\).
   - \(2x + 4y = 8\)
   - Subtract \(2x\) from both sides: \(4y = -2x + 8\).
   - Divide by 4: \(y = -\frac{1}{2}x + 2\).
   - This line crosses the y-axis at \((0, 2)\) and has a slope of \(-\frac{1}{2}\).

#### Instructions for Graphing:

1. **Plot the first line \(y = -2x - 1\)**:
   - Start at the point \((0, -1)\) on the y-axis.
   - From there, use the slope \(-2\) to find another point. For instance, if \(x = 1\), then \(y = -2(1) - 1 = -3\). So, plot the point \((1, -3)\).
   - Draw a straight line through these points.

2. **Plot the second line \(y = -\frac{1}{2}x + 2\)**:
   - Start at the point \((0, 2)\) on the y-axis.
   - From there, use the slope \(-\frac{1}{2}\) to find another point.
Transcribed Image Text:### Solving Systems of Equations by Graphing #### Problem: Solve the system of equations by graphing: \[ \begin{cases} y = -2x - 1 \\ 2x + 4y = 8 \end{cases} \] #### Solution: 1. **Graph the First Equation**: \(y = -2x - 1\) - This is a linear equation in slope-intercept form \(y = mx + b\), where \(m\) is the slope and \(b\) is the y-intercept. - The y-intercept \(b = -1\), which means the line crosses the y-axis at \((0, -1)\). - The slope \(m = -2\) indicates that for every 1 unit increase in \(x\), \(y\) decreases by 2 units. 2. **Graph the Second Equation**: \(2x + 4y = 8\) - First, simplify this equation to the slope-intercept form \(y = mx + b\). - \(2x + 4y = 8\) - Subtract \(2x\) from both sides: \(4y = -2x + 8\). - Divide by 4: \(y = -\frac{1}{2}x + 2\). - This line crosses the y-axis at \((0, 2)\) and has a slope of \(-\frac{1}{2}\). #### Instructions for Graphing: 1. **Plot the first line \(y = -2x - 1\)**: - Start at the point \((0, -1)\) on the y-axis. - From there, use the slope \(-2\) to find another point. For instance, if \(x = 1\), then \(y = -2(1) - 1 = -3\). So, plot the point \((1, -3)\). - Draw a straight line through these points. 2. **Plot the second line \(y = -\frac{1}{2}x + 2\)**: - Start at the point \((0, 2)\) on the y-axis. - From there, use the slope \(-\frac{1}{2}\) to find another point.
**Graphing Inequalities: Example**

Consider the following inequalities:
\[
\begin{cases}
y > x - 1 \\
y < -4x + 1
\end{cases}
\]

### Explanation of the Graph
In the graph, the system of linear inequalities is represented on a Cartesian plane. Here, each point on the plane corresponds to a pair of \( (x, y) \) values.

#### Axes:
- The x-axis (horizontal) ranges from -5 to 5.
- The y-axis (vertical) ranges from -5 to 5.

#### Equations:
1. \( y > x - 1 \)
2. \( y < -4x + 1 \)

### How to Interpret the Graph

1. **Graphing \( y > x - 1 \):**
   - This inequality represents the region above the line \( y = x - 1 \).
   - To identify the line \( y = x - 1 \), note the slope is 1 and the y-intercept is -1.
   - The region above this line (not including the line itself) satisfies the inequality.

2. **Graphing \( y < -4x + 1 \):**
   - This inequality represents the region below the line \( y = -4x + 1 \).
   - To identify the line \( y = -4x + 1 \), note the slope is -4 and the y-intercept is 1.
   - The region below this line (not including the line itself) satisfies the inequality.

### Analyzing the Graph:

The two inequalities intersect, and their combined regions define a specific area in the Cartesian plane.

- Region for \( y > x - 1 \): Above the line \( y = x - 1 \).
- Region for \( y < -4x + 1 \): Below the line \( y = -4x + 1 \).

We intersect these regions to find the area that satisfies both conditions simultaneously. This particular area will lie between these lines where both conditions are met.
Transcribed Image Text:**Graphing Inequalities: Example** Consider the following inequalities: \[ \begin{cases} y > x - 1 \\ y < -4x + 1 \end{cases} \] ### Explanation of the Graph In the graph, the system of linear inequalities is represented on a Cartesian plane. Here, each point on the plane corresponds to a pair of \( (x, y) \) values. #### Axes: - The x-axis (horizontal) ranges from -5 to 5. - The y-axis (vertical) ranges from -5 to 5. #### Equations: 1. \( y > x - 1 \) 2. \( y < -4x + 1 \) ### How to Interpret the Graph 1. **Graphing \( y > x - 1 \):** - This inequality represents the region above the line \( y = x - 1 \). - To identify the line \( y = x - 1 \), note the slope is 1 and the y-intercept is -1. - The region above this line (not including the line itself) satisfies the inequality. 2. **Graphing \( y < -4x + 1 \):** - This inequality represents the region below the line \( y = -4x + 1 \). - To identify the line \( y = -4x + 1 \), note the slope is -4 and the y-intercept is 1. - The region below this line (not including the line itself) satisfies the inequality. ### Analyzing the Graph: The two inequalities intersect, and their combined regions define a specific area in the Cartesian plane. - Region for \( y > x - 1 \): Above the line \( y = x - 1 \). - Region for \( y < -4x + 1 \): Below the line \( y = -4x + 1 \). We intersect these regions to find the area that satisfies both conditions simultaneously. This particular area will lie between these lines where both conditions are met.
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