Download presentation

Presentation is loading. Please wait.

1
**Chapter 3: Parallel and Perpendicular Lines**

3-6 Lines in the Coordinate Plane

2
**Objectives: Student will be able:**

1.To write the equations of lines in slope intercept form 2.To graph lines given their equation HW/CW: pgs 169 #’s 2 – 16, Even

3
Slope-Intercept Form y = mx + b m is the slope b is the y-intercept You need m and b to write the equation!

4
**Write the equation of the line.**

What is the y-intercept? b = -2 What is m? m = 3/2 y = 3/2x -2 x y

5
**Write the equation of the line.**

b = ? b = 1 m = ? m = -1/2 y = -1/2x + 1 x y

6
**Write the equation of the line.**

b = ? b = 4 m = ? m = 0 y = 4 x y

7
**Find the slope and y-int. of each equation.**

1) y = -4x + 3 m = -4 b = 3 2) y = 5 - 1/2x m = -1/2 b = 5 3) 8x + y = 3/4 m = -8 b = 3/4 4) 4x - 2y = 10 m = 2 b = -5

8
**Type 1: Write the equation given the slope and y-intercept**

1) m = -3, b = 1 y = -3x + 1 2) m = -2/5, b = -4 y = -2/5x - 4

9
x- and y-intercepts The x-intercept is the point where a line crosses the x-axis. The general form of the x-intercept is (x, 0). The y-coordinate will always be zero. The y-intercept is the point where a line crosses the y-axis. The general form of the y-intercept is (0, y). The x-coordinate will always be zero.

10
**Finding the x-intercept**

For the equation 2x + y = 6, we know that y must equal 0. What must x equal? Plug in 0 for y and simplify. 2x + 0 = 6 2x = 6 x = 3 So (3, 0) is the x-intercept of the line.

11
**Finding the y-intercept**

For the equation 2x + y = 6, we know that x must equal 0. What must y equal? Plug in 0 for x and simplify. 2(0) + y = 6 0+y = 6 y = 6 So (0, 6) is the y-intercept of the line.

12
**To summarize…. To find the x-intercept, plug in 0 for y.**

To find the y-intercept, plug in 0 for x.

13
**Find the x- and y-intercepts of x = 4y - 5**

x-intercept: Plug in y = 0 x = 4y-5 x = 4(0) - 5 x = 0 - 5 x = -5 (-5, 0) is the x-int. y-intercept: Plug in x = 0 x = 4y-5 0 = 4y - 5 5 = 4y 5/4 = y (0, 5/4) is the y-int.

14
**Find the x- and y-intercepts of y = -3x – 1**

x-intercept Plug in y=0 y = -3x - 1 0 = -3x - 1 1 = -3x -1/3 = x (-1/3, 0) is the x-int. y-intercept Plug in x=0 y = -3(0) - 1 y = 0 - 1 y = -1 (0, -1) is the y-int.

15
**Find the x- and y-intercepts of 6x - 3y =-18**

x-intercept Plug in y=0 6x-3y=-18 6x-3(0) = -18 6x - 0 = -18 6x = -18 x = -3 (-3, 0) is the x-int. y-intercept Plug in x=0 6x-3y=-18 6(0)-3y = -18 0 - 3y = -18 -3y = -18 y = 6 (0, 6) is the y-int.

16
**Find the x- and y-intercepts of x=3**

x-intercept Plug in y=0 There is no y. Why? X=3 is a vertical line so x always equals 3. (3, 0) is the x-int. y-intercept A vertical line never crosses the y-axis. There is no y-int. x y

17
**Find the x- and y-intercepts of y=-2**

x-intercept Plug in y=0 Y cannot = 0 because y=-2. y=-2 is a horizontal line so it never crosses the x-axis. There is no x-int. y-intercept Y=-2 is a horizontal line so y always equals -2. (0,-2) is the y-int. x y

18
**Graphing Equations Example: Graph the equation -5x + y = 2**

Solve for y first. -5x+y=2 Add 5x to both sides. y=5x+2 The equation y=5x+2 is in slope-intercept form, y=mx+b. The y-intercept is 2 and the slope is 5. Graph the line on the coordinate plane.

19
1. Graph y=5x+2 x y

20
**Example :Graph the equation 4x - 3y = 12.**

Graphing Equations Example :Graph the equation 4x - 3y = 12. Solve for y first. 4x-3y=12 Subtract 4x from both sides. -3y = -4x Divide by -3. y = -4/-3 x+ 12/-3. Simplify. y = 4/3 x – 4 The equation y=4/3 x - 4 is in slope-intercept form, y=mx+b. The y-intercept is -4 and the slope is 4/3. Graph the line on the coordinate plane.

21
2. Graph y=4/3 x - 4 x y

Similar presentations

Presentation is loading. Please wait....

OK

EXAMPLE 1 Write an equation of a line from a graph

EXAMPLE 1 Write an equation of a line from a graph

© 2018 SlidePlayer.com Inc.

All rights reserved.

To make this website work, we log user data and share it with processors. To use this website, you must agree to our Privacy Policy, including cookie policy.

Ads by Google