Number of points of intersection of `n` straight lines if `n` satisfies `^n+5P_(n+1)=(11(n-1))/2xx^(n+3)P_n` is a. `15` b. `28` c. `21` d. 10

If ^(n+5)P_(n+1)=(11(n-1))/(2)n+3P_(n), find n

Find n, ""^(n+5)P_(n+1)=(11)/(2)(n-1)*""^(n+3)P_(n).

If ^(2n+1)P_(n-1):^(2n-1)P_(n)=3:5, find n

Straight lines are drawn by joining m points on a straight line of n points on another line. Then excluding the given points, the number of point of intersections of the lines drawn is (no tow lines drawn are parallel and no these lines are concurrent). a. 4m n(m-1)(n-1) b. 1/2m n(m-1)(n-1) c. 1/2m^2n^2 d. 1/4m^2n^2

The number of positive integers satisfying the inequality C(n+1,n-2)-C(n+1,n-1)<=100 is