Graphing Linear Functions in Two Variables

1.5.2 Graphing Linear Functions in Two Variables

1.5.2 • Graphing Linear Functions in Two Variables

Activity

For questions 1 – 7, use the equation 3x+4y=123x+4y=12

1.

Find the value of yy when x=0x=0.

3

2.

Find the value of xx when y=0y=0.

4

3.

Plot both of those points on a coordinate grid and use a ruler to draw a line.

Compare your answer:

A plot of the x and y coordiantes of the equation 3x + 4y =12.
4.

What is the coordinate of the xx-intercept?

Compare your answer:

(4,0)(4,0)

5.

What is the coordinate of the yy-intercept?

Compare your answer:

(0,3)(0,3)

6.

What are two other names for the xx-intercept?

Compare your answer:

zero, solution

7.

What is the slope of the line?

−34−34

Self Check

Graph the equation 5x−2y=105x−2y=10. Which of the following describes the intercepts and slope of the graph?

  1. xx-intercept: x=−5x=−5; yy-intercept: y=2y=2; Slope: 5252
  2. xx-intercept: x=2x=2; yy-intercept: y=−5y=−5; Slope: 5252
  3. xx-intercept: x=−2x=−2; yy-intercept: y=5y=5; Slope: −52−52
  4. xx-intercept: x=2x=2; yy-intercept: y=−5y=−5; Slope: 5252

Additional Resources

Graphing a Line and Describing Characteristics

There are many ways to graph an equation of a line. One way is to use the xx-intercepts and yy-intercepts as two points on the line.

Example

Graph 3x−6y=183x−6y=18 using the intercepts, then identify key characteristics.

Step 1 - Find the xx-intercept.
To find the xx-intercept, let y=0y=0.

3x−6y=183x−6(0)=183x=18x=63x−6y=183x−6(0)=183x=18x=6

(6,0)(6,0) is the xx-intercept
The xx-intercept is also called a solution or zero.

Step 2 -Find the yy-intercept.
To find the yy-intercept, let x=0x=0.

3x−6y=183(0)−6y=18−6y=18y=−33x−6y=183(0)−6y=18−6y=18y=−3

(0,−3)(0,−3) is the yy-intercept

Step 3 -Graph the line by connecting the yy-intercepts.

A plot of y intercepts of the equation 3x - 6y =18.

Step 4 - Find the slope of the line.

slope=riserun=36=12slope=riserun=36=12

Try it

Graphing a Line and Describing Characteristics

For questions 1 – 2, use the equation 7x−3y=217x−3y=21.

1.

Graph the equation using the intercepts.

Compare your answer:

Answer:

Graph of the equation 7x - 3y = 21.
2.

What is the slope of the line?

7373