persamaan garis yg melalui titik(1,2) dan tegak lurus garis y,=-3x+5 adalah

m1 × m2 = -1
m1 = -3
-3 × m2 = -1
m2 = -1 : -3
m2 = -1 × -1/3

y = mx + c
y = 2
x = 1
2 = 1/3 (1) + c
2 = 1/3 + c
2 - 1/3 = c
6/3 - 1/3 = c
c = 5/3 // 1 2/3

persamaan garis..
y = 1/3x + 1 2/3