Question

if n straight lines in a plane are such that no two oif them are parallel and no three of them are concurrent , prove that they intersect each other in [n(n-1)] /2 points.

Answer 1

Dear Student,
let try draw lines one by one.

1st line - 0 points
2nd line - new 1 point
3td line - new 2 points + old 1 point
4th line - new 3 points + old 2+1 points
5th line - new 4 points + old 3+2+1 points
n-th line - (n-1) points + (n-2) .... 3+2+1

therefore, S=1+2+3...(n-1)

S=(n-1)n/2
Regards