Question

for what value of a are the points collinear (1,2) (-5,6) and (a,-2)

Answer 1

Answer:

(7)

Step-by-step explanation:

We have 3 collinear points

A (1 ,2) ; B(-5,6) , C (a,-2)

If the situation is following,

A ( x1 , y1) ; B(x2 ,y2 ) ; C(x3,y3) are collinear then,

x1(y2-y3) + x2 (y3 - y1) + x3(y1-y2) =0

so ,

$1(6 + 2) - 5( - 2 - 2) + a(2 - 6) = 0$

$so \\ 4a + 8 + 20 = 0 \\ therefore \: \\ a = 7$