1.

Two straight lines intersect at a point O. Points A_1, A_2 ..., A_n are taken on one line and points B, B_2, ..., B_n, on the other. If the point O is not to be used, then the number of triangles that can be drawn using these points as vertices, is

Answer»

`""^(N)C_2+""^(m)C_2`
`""^(2N)C_2`
`""^(m+n)C_2`
NONE of these

Answer :D


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