persamaan garis yang melalui satu titik P(-1,2)dengan gradien 1/2 adalah..

m = 1/2

y - y1 = m(x - x1)
y - 2 = 1/2 (x - (-1)) [×2]
2y - 4 = x + 1
0 = x + 1 - 2y + 4
0 = x - 2y + 5
x - 2y + 5 = 0

y-y1 = m(x-x1)
y-2 = 1/2(x-(-1))
y-2 = 1/2(x+1)
y-2 = 1/2x + 1/2
y = 1/2x + 2 1/2
y = 1/2x + 5/2