Question

Find the value of k for which points
P(k,-1),Q(2,1) and R(4,5) are collinear.​

Answer 1

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

here, x1= k y1 = -1 x2 = 2 y2 = 1 x3 = 4 y3 = 5

k ( 1 - 5 ) + 2 ( 5 - {- 1}) + 4 ( - 1 - 1 ) = 0

= k ( - 4) + 12 - 8 = 0

= - 4 k + 4 = 0

k = - 4 / - 4 = 1

so, the value of k is 1..