Question

The centroid of a triangle ABC is at the point (1, 1, 1). If the coordinates of A and B are (3, –5, 7) and (–1, 7, –6) respectively, find the coordinates of the point C.

Answer 1

Let G be the centroid of\[∆\]ABC.
Given: G\[\equiv \left( 1, 1, 1 \right)\]

Let C\[\equiv \left( x, y, z \right)\]

\[\text{ Then }, 1 = \frac{3 - 1 + x}{3}\]
\[ \Rightarrow 3 = 3 - 1 + x \]
\[ \Rightarrow 3 = 2 + x \Rightarrow x = 1\]
\[\text{ and } 1 = \frac{- 5 + 7 + y}{3} \]
\[ \Rightarrow 3 = 2 + y \]
\[ \Rightarrow y = 1\]
\[\text{ and } 1 = \frac{7 - 6 + z}{3}\]
\[ \Rightarrow 3 = 1 + z\]
\[ \Rightarrow z = 2\]

\[\therefore C \equiv \left( 1, 1, 2 \right)\]