Question

Find he values of p which the points (-1,-1), (2,p) and (8,11) are collinear

Answer 1

If the points are collinear then the area of traingle formed by them will be equal to zero

½*|-1(p-11)+2(11+1)+8(-1-p)| = 0
½*|-p+11+24-8-8p| = 0
½*|-9p+27| = 0
|-(9p-27)|=0
9p-27=0
9p=27
p=3


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