tolong ya kk.. nomer 1 dan 2

1. a.
BD² = AD x CD
4² = 2√5 x CD
16 = 2√5 x CD
CD = 16 / 2√5
CD = 16√5 / 10
CD = 8√5 / 5 cm

1.b
BC² = CD x AC
BC² = 8√5 / 5 x (2√5 + 8√5 / 5)
BC² = 8√5 / 5 x 18√5 / 5
BC² = 144/5
BC = √144/5
BC = 12√5 / 5 cm

1.c.
AB² = AD x AC
AB² = 2√5 x 18√5 / 5
AB² = 36
AB = √36
AB = 6 cm

1.d.
AC = AD + CD
AC = 2√5 + 8√5 / 5
AC = 18√5 / 5 cm

2.
EF / DE = BC / AB
EF / 12 = 20 / 18
EF / 12 = 10/9
EF = 10/9 x 12
EF = 40/3 cm

DF / DE = AC / AB
DF / 12 = 24 / 18
DF / 12 = 4/3
DF = 4/3 x 12
DF = 16 cm

1)
AD = 2V5 cm
BD = 4 cm
a) CD
b) BC
c) AB
d) AC

a)
(BD)^2 = AD × CD
4^2 = 2V5 × CD
16 = 2V5 × CD
CD = 16/(2V5)
CD = [16/(2V5)] × [(2V5)/(2V5)]
CD = (32V5)/20
CD = (8V5)/5 cm

b)
(BC)^2 = CD × CA
(BC)^2 = (8V5)/5 × [(8V5)/5 + (2V5)]
(BC)^2 = (8V5)/5 × [(8V5)/5 + (10V5)/5]
(BC)^2 = (8V5)/5 × (18V5)/5
(BC)^2 = 720/25
(BC)^2 = 144/5
BC = V(144/5)
BC = 12/V5
BC = (12/V5) × (V5 × V5)
BC = (12V5)/5 cm

c)
(AB)^2 = AD × AC
(AB)^2 = 2V5 × (18V5)/5
(AB)^2 = 36
AB = V36
AB = 6 cm

d)
AC = AD + CD
AC = 2V5 + (8V5)/5
AC = (10V5)/5 + (8V5)/5
AC = (18V5)/5 cm


2)
a)
EF/BC = DE/AB
EF/20 = 12/18
EF × 18 = 12 × 20
18EF = 240
EF = 240/18
EF = 13 6/18
EF = 13 1/3 cm

b)
DF/AC = DE/AB
DF/24 = 12/18
DF × 18 = 12 × 24
18DF = 288
DF = 288/18
DF = 16 cm