Day 6 Problems 22608

1
Day 6 Problems 2/26/08

• Graph each equation.
• 1. y 2 (x 3) 2. y 3 -2(x 1)
• Write an equation in point-slope form for the
  line through the given point with the given
  slope.
• 3. (4 , 2) m 3 4. (-5 , 2) m 0
• A line passes through the given points. Write an
  equation for the line in point-slope form. Then
  rewrite the equation in slope-intercept form.
• 5. (-1 , 0) , (1 , 2)

2
6.5 Parallel and Perpendicular Lines 2/27/08

• Parallel lines lines in the same plane that
  never intersect.

3
Slopes of Parallel Lines

• Nonvertical lines are parallel if they have the
  SAME SLOPE and DIFFERENT Y-INTERCEPTS. Any two
  vertical lines are parallel.
• Example The equations y 2x 1 and y 2x
  3 have the same slope, 2, and different
  y-intercepts. The graphs of the two equations
  are parallel.

4
Determining Whether Lines are Parallel

• Are the graphs of and
  2x 6y 12 parallel? Explain.
• Write 2x 6y 12 in slope-intercept form. Then
  compare with
• The lines are parallel. The equations have the
  same slope, , and different
  y-intercepts.

5
Writing Equations of Parallel Lines

• Write an equation for the line that contains (5 ,
  1) and is parallel to
• Step 1 Identify the slope of the given line.
• Step 2 Write an equation of the line through (5
  , 1) using point-slope form, then change to
  slope-intercept.

6
Perpendicular Lines

• Perpendicular lines lines that intersect to
  form right angles.
• SLOPES OF PERPENDICULAR LINES
• Two lines are perpendicular their slope is the
  opposite reciprocal of the given slope. A
  vertical and horizontal line are also
  perpendicular.
• EXAMPLE the slope ofis The slope of y
  4x 2 is 4.

7
Negative Reciprocal

• The product of two numbers is -1 if one number is
  the negative reciprocal of the other.
• How to find the negative reciprocal of a number
• Start with Find its Write the
• a fraction reciprocal neg. reciprocal
• Start with Find its Write its
• an integer reciprocal neg. reciprocal

8
Writing Equations for Perpendicular Lines

• Find an equation of the line that contains (0 ,
  -2) and is perpendicular to y 5x 3.
• Step 1- Identify the slope of the given line.
• m 5
• Step 2 Find the negative reciprocal of the
  slope
• Step 3 Use the slope-intercept form to write an
  equation.

9
More Practice!!!

• Textbook p. 314 2 40 even.
• Homework Worksheet 6.5.