Suatu garis lurus melewati titik (-1,4) dan (2,5). Tentukan persamaan garisnya !!

( y - y1) / (y2 - y1) = ( x - x1) / ( x2 - x1)
( y - 4) / (5 - 4 ) = ( x + 1) / ( 2 + 1)
( y - 4 ) / 1 = ( x + 1) / 3
3 ( y - 4) = 1 ( x + 1)
3y - 12 = x + 1
3y - x = 1 + 12
3y - x = 13

pers garis lurus : 3y - x = 13