Post on 31-Dec-2015
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