Question

The value of p for which the points $(-1,3),(2,p)$ and $(5,-1)$ are collinear then p is

• A. $-1$
• B. $2$
• C. $1$
• D. $-2$

Answer 1

The correct option is C $1$

For collinearity of points $A(-1,3),B(2,p),C(5,-1)$, area of $\Delta ABC$ should be zero ,i.,e,
$\frac{1}{2}|(p-1)+2(-1-3)+5(3-p)|=0$
$\Rightarrow p-1-8+15-5p=0$
$\Rightarrow -6p+6=0$

$\Rightarrow -6p=-6$

$\Rightarrow p=1$