coordinate geometry

Asked by  | 26th Sep, 2008, 05:52: PM

Expert Answer:

 If the area of quadrilateral is zero

 So the area of the sum of the two triangles formed by joining the vertices (1,2)  and (7 , -4)

1/2 [ 1(6+4)-5 (-4-2) + 7 (2 -6) + 7(-2-2) + k (2 +4) +1 ( -4 + 2)]  =  0

1/2 [ 10 + 80 - 28 -28 + 6k -2 ] = 0

-18 + 6k = 0

k = 3

Answered by  | 26th Sep, 2008, 06:50: PM

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