Pre-Calc w/Trig

Problem of the Day

Find the Slope and y-intercept of the following

4(y – 6) + 8y – 2x = 4(y – 5)

Answer: y = ¼ x + ½ So m = ¼ and b = ½

Pre-Calc w/Trig

Lesson 1.4 B

Objectives: SSBAT write the equation of a line given a point and

the slope or 2 points on the line.SSBAT write the equation of a line parallel or

perpendicular to a given line and given a point.

Standards: M11.A.2.2.1, M11.D.2.1.3, M11.D.3.2.2

Writing an Equation given the Slope and Y-intercept

Substitute the slope and y-intercept into the equation y = mx + b for m and b

Write the equation of each line with the given slope and y-intercept. (y = mx + b)

1. Slope is and y-intercept is 11

m b

y = x + 11

2. Slope is -9 and y-intercept is -4

m b

y = -9x – 4

Point-Slope Form of the Equation of a Line

Used to write the equation of a line given1) A point on the line and the slope2) 2 points on the line

y - y1 = m(x - x1)

Where m is the slope and (x1 , y1) is a point on the line

1. Find the equation of the line containing the point (1,-2) and having a slope of 3. Write your answer in slope- intercept form.

y - (- 2) = 3(x - 1)

y + 2 = 3x – 3

y = 3x – 5

2. Find the equation of the line containing the point (-8, 5) and having a slope of ½ . Write your answer in slope-intercept form.

y - (5) = ½ (x - -8)

y - 5 = ½ x + 4

y = ½ x + 9

3. Find the equation of the line containing the points (8 , -1) and (2 , 5)

Write your answer in slope-intercept form.

1st find the slope of the line through the points 2nd choose one point and use point-slope form

1 6

6

82

)1(5

m

)8(1)1( xy

81 xy

7 xy

Equation of Horizontal Liney = #

Equation of Vertical Linex = #

Remember: Horizontal Line Slope is 0

Vertical Line Slope is Undefined

1. Write the equation of the line through the points (-3, 8) and (7, 8)

)3(7

88

m10

0m

Slope of 0 Horizontal Line

Equation of Horizontal Line y = #

The number is the y-coordinate of the point it goes through

Equation of Line is

y = 8

0m

2. Write the equation of the line through the points (5, 4) and (5, -7)

55

47

m0

11m

Slope is UNDEFINED Vertical Line

Equation of Vertical Line x = #

The number is the x-coordinate of the point it goes through

Equation of Line is

x = 5

On Your Own.Write the equation of each line. Write your answer in slope-intercept form.

1. Through the points (4, -1) and (1, 5)

2. Perpendicular to the line y = 5/2 x + 7 and through (-4, 0)

y = -2x + 7

5

8

5

2 xy 6.1

5

2 xyor

No Homework

Day 2 – In Class Page 40 – 41 #17 – 24 All

#25, 27, 30 #36 – 41 All