數學.............................................圈住果條

18. Let Y be (x,y)
-1 = [x+2(-3)] / (1+2) = (x-6)/3
-3 = x-6
x=3
2 = [y+2(1)] / (1+2) = (y+2)/3
6 = y+2
y = 4
The answer is C (3,4)

19. Note that triangle ABC is similar to triangle ADE. (A.A.A.)
As BC:DE = 1:4, AB: AD = 1: 4 (corr. angles, ~triangles)
Hence, AB:BD = 1:3
Let D be (x,y)
2 = [x+3(4)]/(1+3)
2 = (x+12)/4
8 = x+12
x = -4
3 = [y+3(6)]/(1+3)
3 = (y+18)/4
12 = y+18
y = -6
Hence the answer is B (-4,-6)