tentukan persamaan garis dan gradien yang melalui titik titik berikut! a. (12,8) dan (4,5) b. (-1,5) dan (-3,2)

a. (12, 8) dan (4, 5)
x1 = 12
y1 = 8
x2 = 4
y2 = 5

(y - y1)/(y2 - y1) = (x - x1)/(x2 - x1)
(y - 8)/(5 - 8) = (x - 12)/(4 - 12)
(y - 8)/(-3) = (x - 12)/(-8)
-8(y -8) = -3(x - 12)
-8y + 64 = -3x + 36
-8y = -3x + 36 - 64
-8y = -3x - 28
y = 3/8 x + 7/4

gradien = 3/8

b. (-1, 5) dan (-3, 2)
x1 = -1
y1 = 5
x2 = -3
y2 = 2

(y - y1)/(y2 - y1) = (x - x1)/(x2 - x1)
(y - 5)/(2 - 5) = (x - (-1))/(-3 - (-1))
(y - 5)/(-3) = (x + 1)/(-2)
-2(y - 5) = -3(x + 1)
-2y + 10 = -3x - 3
-2y = -3x -3 - 10
-2y = -3x - 13
y = 3/2 x + 13/2

gradien = 3/2