persamaan garis melalui titik(4,-1) dan (5,3)

( y - y1 ) / ( y2 - y1 ) = ( x - x1 ) / ( x2 - x1 )
( y + 1 ) / ( 3 + 1 ) = ( x - 4 ) / ( 5 - 4 )
( y + 1 ) / 4 = ( x - 4 ) / 1
1 ( y + 1 ) = 4 ( x - 4)
y + 1 = 4x - 16
y - 4x = - 16 - 1
y - 4x = - 17

gradien (m) = 3 + 1 / 5 -4 
4/1
4

y - y1 = m ( x -x1)
y - 1 = 4 ( x - 5)
y - 1 = 4x - 20
y = 4x - 20 + 1
y = 4x - 19