Math Problem Statement

Graph the equation y = 3x + 8 by hand by plotting points. Verify your results using a graphing utility.

Solution

The equation you provided is y=3x+8y = 3x + 8, which is in slope-intercept form: y=mx+by = mx + b, where:

  • m=3m = 3 is the slope,
  • b=8b = 8 is the y-intercept (where the line crosses the y-axis).

Steps to graph by hand:

  1. Start with the y-intercept:

    • Plot the point (0,8)(0, 8) on the y-axis because when x=0x = 0, y=8y = 8.
  2. Use the slope to find another point:

    • The slope is 3, which means "rise over run." A slope of 3 can be written as 31\frac{3}{1}, meaning for every 1 unit you move to the right (positive direction on the x-axis), move 3 units up (positive direction on the y-axis).
    • Starting from (0,8)(0, 8), move 1 unit to the right (to x=1x = 1) and 3 units up (to y=11y = 11). Plot this point: (1,11)(1, 11).
  3. Draw the line:

    • Draw a straight line through the points (0,8)(0, 8) and (1,11)(1, 11).
    • You can also extend the line to cover more values by plotting additional points using the slope.

Verifying using a graphing utility:

You can input the equation y=3x+8y = 3x + 8 into any graphing calculator or online graphing tool (such as Desmos) to verify that the line you plotted matches the graph generated by the utility.

Would you like a more detailed breakdown or any clarifications?

Here are 5 related questions for practice:

  1. What would the graph look like if the slope were negative?
  2. How would you graph y=3x+8y = 3x + 8 if you were given only the slope and a point not on the y-axis?
  3. How do you find the slope if you are given two points?
  4. How does changing the value of bb affect the graph of a linear equation?
  5. What is the equation of a line parallel to y=3x+8y = 3x + 8?

Tip: The y-intercept helps you quickly plot the starting point of the line on the graph, and the slope tells you how to move from that point.

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Math Problem Analysis

Mathematical Concepts

Linear Equations
Graphing
Slope-Intercept Form

Formulas

Slope-Intercept Form: y = mx + b
Slope formula: m = rise/run

Theorems

Linearity of Linear Equations

Suitable Grade Level

Grades 7-10