Writing Equations of Lines

Do Now: Answer each of the following questions based on the graph

1. What is the slope of the line?

2. What is the y-intercept?

3. What is the equation of the line?

How do we write equations of lines?

1. Determine the slope

2. Determine the y-intercept

3. Sub slope (m) and y-intercept (b) into

y = mx + b

Practice:

1. What is the slope of the line?

2. What is the y-intercept?

3. What is the equation of the line?

Practice:

1. What is the slope of the line?

2. What is the y-intercept?

3. What is the equation of the line?

How do we write equations of lines without the graph?

1. Example: Write an equation of the line whose slope is 3 and passes through the point (1,4).

1. What is slope (m)?

2. To find y-intercept:

a. Sub m, x and y into y=mx +b

b. Solve for b

3. Sub m and b into y=mx +b

Practice

2. Example: Write an equation of the line whose slope is - 2 and passes through the point (2,-3).

1. What is slope (m)?

2. To find y-intercept:

a. Sub m, x and y into y=mx +b

b. Solve for b

3. Sub m and b into y=mx +b

How do we write equations of lines without the graph?

3. Example: Write an equation of the line that passes through the points (2,6) and (-2,10).

1. Find slope (m) using slope formula

2. To find y-intercept, pick one of the points given:

a. Sub m, x and y into y=mx +b

b. Solve for b

3. Sub m and b into y=mx +b

Practice:

4. Example: Write an equation of the line that passes through the points (-1,-2) and (2,10).

1. Find slope (m) using slope formula

2. To find y-intercept, pick one of the points given:

a. Sub m, x and y into y=mx +b

b. Solve for b

3. Sub m and b into y=mx +b

How do we write equations of lines without the graph?

5. Write the equation of a line whose slope is - 3 and

y-intercept is 1.

1. Find slope (m)

2. Find y-intercept (b)

3. Substitute into y=mx+b

Practice

6. Write the equation of a line whose slope is 1/2 and

y-intercept is -3.

1. Find slope (m)

2. Find y-intercept (b)

3. Substitute into y=mx+b

Practice

7. What is the equation of the line that is parallel to y - 2x = 4 and whose y-intercept is –1?

1. Find slope (m)

2. Find y-intercept (b)

3. Substitute into y=mx+b

Practice

8. What is the equation of the line that is parallel to y + 3x = 2 and whose y-intercept is 4?

1. Find slope (m)

2. Find y-intercept (b)

3. Substitute into y=mx+b

Practice

9. Write an equation of the line that is perpendicular to

y = 2x + 4 and whose

y-intercept is 2?

1. Find slope (m)

2. Find y-intercept (b)

3. Substitute into y=mx+b

Practice

10.Write an equation of the line that is perpendicular to

y = ½ x - 2 and whose

y-intercept is 1?

1. Find slope (m)

2. Find y-intercept (b)

3. Substitute into y=mx+b