Question

If the x-co-ordinate of a point P on the join of Q (2, 2, 1) and R (5, 1, –2) is 4, then its z-co-ordinate is

• A. 2
• B. 1
• C. –1
• D. –2

Answer 1

Answer: (C)

–1

Answer 2

Let the point P be $\left( \frac { 5 k + 2 } { k + 1 } , \frac { k + 2 } { k + 1 } , \frac { - 2 k + 1 } { k + 1 } \right)$.

∵ Given that $\frac { 5 k + 2 } { k + 1 } = 4$

⇒ $k = 2$

∴ z-co-ordinate of $P = \frac { - 2 ( 2 ) + 1 } { 2 + 1 } = - 1$