Question

if points A(a,-11) B(9 ,-9) and C(18, -3) are collinear, find the value of a​

Answer 1

Step-by-step explanation:

If the points of a triangle are Collinear then area of the triangle is 0 so,ar(ABC)=0.

1/2[a(-9+3)+9(-3+11)+18(-11+9)]=0

1/2[-6a+72-36]=0

1/2[-6a+36]=0

-3a+18=0

a=6