Question

Show that the points $A(4,2)$, $B(7,5)$, $C(9,7)$ are collinear.

Answer 1

$A(4,2),B(7,5),C(9,7)$

Area of $△ABC$

$\frac{1}{2}$ $$\left|\begin{array}{ccc}4& 2& 1\\ 7& 5& 1\\ 9& 7& 1\end{array}\right|$$ = \dfrac {1}{2}| 4(-2) - 2(-2) + (4)|$

$=0$

Area of $△ABC=0$ so the points should be collinear.