Question

determine if the points(1,5),(2,3),and (-2,-11) are collinear

Answer 1

let A(1,5) B(2,3) C(-2,-11)
slope of AB = y2-y1/x2-x1
3-5/2-1
-2
slope of BC -11-3/-2-2
-14/-4
14/4
7/2
As slopes differ the points aren't collinear.

Answer 2

$\bf\huge\boxed{\boxed{\bf\huge\:Hello\:Mate}}}$

$\bf\huge Let A(1 , 5) , \: B(2 , 3) , \: C(-2 , -11)$

$\bf\huge AB= \sqrt{(2 - 1)^2 + (3 - 5)^2}$

$\bf\huge = \sqrt{1^2 + (-2)^2}$

$\bf\huge = \sqrt{1 + 4} = \sqrt{5}$

$\bf\huge BC = \sqrt{(-2 - 2)^2 + (-11 - 3)^2}$

$\bf\huge BC = \sqrt{(-4)^2 + (-14)^2}$

$\bf\huge BC = \sqrt{16 + 196}$

$\bf\huge BC = \sqrt{212}$

$\bf\huge AB = \sqrt{4\times 53} = 2\sqrt{53}$

$\bf\huge AC = \sqrt{(-2 - 1)^2 + ( - 11 - 5)^2}$

$\bf\huge AC = \sqrt{(-3)^2 + (- 16)^2}$

$\bf\huge AC = \sqrt{9 + 256} = \sqrt{265}$

$\bf\huge Hence \:A , B\: and \:C\: are\: not\: collinear$

$\bf\huge\boxed{\boxed{\:Regards=\:Yash\:Raj}}}$