Tiga titik memiliki koordinat A(8,a), B(-1,2) dan C(3,10). Cari nilai a jika luas ABC 12 units²

segitiga

x____y

3____10

-1____2

8____a

3____10

Luas ABC = 12 su

1/2 (3.2 + (-1).a + 8.10 – 10.(-1) – 2.8 – a.3) = 12

6 – a + 80 + 10 – 16 – 3a = 12 × 2

80 – 4a = 24

4a = 80 – 24

4a = 56

a = 56/4

a = 14

Nilai a = 14