 # Drill #19 Determine the value of r so that a line through the points has the given slope: 1. ( 2 , r ) , ( -1 , 2 ) m = -½ Find the slope of the following.

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Drill #19 Determine the value of r so that a line through the points has the given slope: 1. ( 2 , r ) , ( -1 , 2 ) m = -½ Find the slope of the following lines. Determine whether they are parallel, perpendicular, or neither: 2. y = 3x – x + 2y = 6 y = -3x x = 1 – 6y

Drill #20 Find the slope intercept form of the following lines:
1. x + 2y = x + ½ y = 9 3. Find the slope intercept form of the line passing through (1, 3) with a slope of 2. (Write the equation in point-slope for and solve for y.)

Drill #21 Identify which of the following lines are parallel:
1. x + 2y = 6 y = - ½x + 2 4y = 3 – 2x 4x - 8y = -10 2. Write an equation in slope intercept form parallel to y = 2x – 1 and passing through the point (1, 2). 3. Write an equation in slope intercept form perpendicular to 3x – 2y = 3 and passing through the point (3, -2).

Drill #23 Find the slope of the following lines and then determine which are parallel: 1. y = 2x + 3 y – 3 = 3(x + 1) 2x – y = 1 3y = 6x + 4 y = 3 y = ¾ 2. Write an equation in slope intercept form parallel to y = ½ x – 1 and passing through the point (4, 6). 3. Write an equation in slope intercept form perpendicular to y = ½ x – 1 and passing through the point (4, 6).

2-4 Writing Linear Equations
Objective: To write an equation of a line in slope intercept form given the slope and one or two points, and to write an equation of a line that is parallel or perpendicular to the graph of a given equation.

Slope-Intercept Form Definition: An equation in the form of y = mx + b
where m = slope and b = y- intercept In order to write an equation in slope-intercept form you need to know the slope (m) and the y- intercept (b)

Classwork Use the Standard Form formulas: Y-intercept = C/B
Slope = -A/B To complete 2-4 Practice #1-4

Classwork 2-4 Practice #9 – 17 (ODD)

Writing Equations in Slope Intercept Form*
Write the equation of the line with given slope and y- intercepts: Ex1: m = 5 b = ¾ 1A: m = b = 1B: m = 0 b = 0

Point Slope Form * Point Slope Form: An equation in the form of where
Are the coordinates of a point on the line and m is the slope of the line. NOTE: For point slope form we need a point and the slope (or two points).

Point Slope Examples Find the equation of the line (in point-slope form): Ex2. m = 2 and passes through (2, -3) 2A. m = ½ and passes through (-2, 5)

Find the Equation of a Line in Slope Intercept Form*
Passing through a point (x1, y1) with slope m: Method 1: 1. Substitute the point (x1, y1) and the slope m into the formula y = mx + b 2. Solve for b. 3. Substitute m and b into y = mx + b formula Method 2: 1. Write the equation in Point Slope form. 2. Solve for y

Finding the equation of a line
Find the slope-intercept form of a line that has a slope of and passes through (-6, 1). m = ? b = ? Method 1 Substitute m into the equation y = mx + b. Substitute (-6, 1) for x and y in the equation. Solve for b. Once you know m and b you can put the equation in slope-intercept form.

Method 2: Point Slope to Slope Intecept
Convert the point-slope equation into slope-intercept. To convert to slope-intercept form, solve the equation for y.

Classwork 2-4 Practice #9 – 17 (ODD)

Write the Equation of a Parallel or Perpendicular Line*
1st Determine the slope of the line. If finding a parallel line use the same slope as the line If finding a perpendicular line use the negative reciprocal slope 2nd Write the equation in Point Slope form 3rd Convert to Standard or Slope-Intercept Form

Find the equation of the line* EXAMPLE 1
That passes through (-9, 5) and is perpendicular to the line whose equation is y = -3x + 2 Find the perpendicular slope Use the point (point- slope form) to find the equation of the line

Parallel/Perpendicular Examples
Find the equation of the line (in slope-intercept form): 1A. Parallel to y = 3x – 1 and passes through (2, -3) 1B. Perpendicular to 2x – y = 10 and passing through (-1, -2)

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