persamaan garis melalui titik (2,-1)dan tegak lurus garis y=2x+5

Y = 2x + 5
M = 2
karena tegak lurus maka M = -1/2

Y- Y1 = M (X - X1)
Y- (-1) = -1/2 (X - 2)
Y + 1 = -1/2x + 1
______________ x 2
2Y + 2 = -X + 2
2Y + 2 - 2 + X = 0
2Y + X = 0