Question

Find the value of $x$ which the points $(x,-1)$, $(2,1)$ and $(4,5)$ are collinear.

Answer 1

$\text{If}A\left(x,-1\right),B\left(2,1\right)\&C\left(4,5\right)\text{are}$ col liner .

Then slope BC=slope AC

$\Rightarrow \frac{5-1}{4-2}=\frac{5+1}{4-x}$

$\Rightarrow \frac{4}{2}=\frac{6}{4-x}$

$\Rightarrow 16-4x=12$

$\Rightarrow x=1$