math
posted by Madi on .
How many people were at a party if There were 105 handshakes at a party and if each person at the party shook hands with exactly once with every other person. The answer is 15. How do I write the problem?

n(n1)/2=105, > n^2n210=0, n^215n+14n210=0, > n(n15)+14(n15)=0, >(n15)(n+14)=0, so, n=15, =14 , as ve is not possible, so n=15, ans will be 15 men