Question

2^n[1.3.5........(2n-1)]/n!=​

Answer 1

Answer:

2 points are required for a line , so from 20 points total no. of lines are 20C2.

but 4 points are linear so lines formed from these 4 points would be identical.

so substract 4C2 from total.

hence answer is 20C2 - 4C2 +1 .

20*19/2 - 4*3/2 +1

190 - 6 +1

185