Bayangan garis 3x + 5y - 7=0 jika didilatasikan dengan pusat (2,-1)dengan skala -2 adalah

jawab
P(a,b)= (2,-1)
skala = k = - 2

x' = k(x -a) + a
x' = -2(x -2) + 2
x' = -2x +4 + 2
x' = - 2x + 2
2x = 2 - x'
x = 1 - 1/2 x'  (i)

y' = k(y-b) + b
y' = -2(y +1) - 1
y' = -2y - 2 - 1
y'  = -2y - 3
2y = -y' - 3
y = - 1/2 y' - 3/2 ..(ii)

(i) dan (ii) substitusi ke 3x + 5y -7 = 0
3(1 - 1/2 x') + 5(-1/2y' - 3/2) - 7 = 0
3 - 3/2 x  - 5/2 y - 15/2 - 7 =0 }}kalikan 2
6 - 3x - 5y - 15 - 14 = 0
-3x - 5y - 23 = 0
3x + 5y + 23 = 0