Well coolduderama17(this question took some hardwork)
from n points in the plane we select 2 points join them
a line line is formed we then select two lines and we get a point of intersection
and then minus the extrapoints formed (they will be the same i.e the n points which we
will get by intersection of different lines).
from here
(nC2)C2-n.(n-1)C2
solve and get n(n-1)(n-2)(n-3)/8=3(nC4)
3(nC4)is just a trap so dont fall into it
Moderation Team
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