pada segitiga BC ,panjang AB:BC:AC=2:4:5 dan Keliling=44, hitunglah luas BC

Bab Segitiga
Matematika SMP Kelas VII

Segitiga ABC
keliling = AB + BC + AC = 44
2a + 4a + 5a = 44
11a = 44
a = 44 : 11
a = 4

AB = 2 x as
AB = 2 x 4
AB = 8

BC = 4 x a
BC = 4 x 4
BC = 16

AC = 5 x a
AC = 5 x 4
AC = 20

s = 1/2 x (8 + 16 + 20)
s = 22

luas = √( s (s - a) (s - b) (s - c))
luas = √(22 (22 - 8) (22 - 16) (22 - 20))
luas = √(22 x 14 x 6 x 2)
luas = 4√231