Mohon bantuannya yg B.

jawab

dilatasi 
[P(a,b) ,k]
x' = k(x - a) + a
y' = k(y - b) + b

4. 
B(x,y) = (2, -4)
P(a,b) = (a.b)
k = -2
B' (x'y') = (8 ,-1)

x' = k(x -a) + a
8 = -2(2 - a) + a
8 = -4 + 2a + a
12= 3a
a= 4

y' = k(y-b) + b
-1 = -2(-4-b)+ b
-1 = 8 + 2b + b
-9 = 3b
b= - 3

P(a,b) = (4,- 3)

5. 
y = 3x - 4  dilatasi  [P(4,-3) , 4]

x' = k (x - a) + a
x' = 4 (x - 4) + 4
x' = 4x - 12 → x = 1/4 (x' -12)

y' = k(y-b) + b
y' = 4(y+3) - 3
y' = 4y + 9 →  y = 1/4 (y' -9)

substitusi  
y  = 3x - 4
1/4 (y' -9) = 3(1/4)(x' -12)....kali 4
y' - 9 = 3(x'-12)
y' - 9 = 3x - 36
y = 3x - 27