October 16

Finding Equations

1.) Use Slope Intercept

y = mx + b

m = slope
b = why intercept

2.) Point-Slope form

y - y1 = m ( x - x1)

m = 3 P(7, 36)

y - 36 = 3 (x - 7)
y - 36 = 3x - 21
y = 3x - 21 + 36
y = 3x + 15 ---> slope intercept form ( y = mx + b)

Ax + By + C = 0 ---> standard form
3x - y + 15 = 0 ---> (Ax always have to be positive)



Example:

D(6, 1) E (-4, -3)
D(x1, y1) E (x2, y2)

1.) Find the slope

Y2 - Y1
_____
m =
X2 - X1


(-3) - (1)
______
m =
(-4) - (6)


m = -4/-10

m = 2/5

2.) Use point-slope form

y - y1 = m (x - x1)
y - (-3) = 2/5 [x - (-4)]
5 (y + 3) = [2/5 (x + 4)] 5
5y + 15 = 2x + 8

Ax + By + C = 0

2x - 5y - 7 = 0

P(13, -15) m = -7/2

y - y1 = m ( x - x1)

y - (-15) = -7/2 (x - 13)
2(y + 15) = [-7/2 (x - 13)]2
2y + 30 = -7x + 91

Ax + By + C = 0 (standard form)
7x + 2y - 61 = 0

Do exercise 15, 1 - 12

Sorry if this is posted a day late. I had some difficulties with my interent.
next post is jlavina