m points on one straight line are joined to n points on another straight line. The number of points of intersection of the line segments thus formed is (A) `^mC-2.^nC_2` (B) `(mn(m-1)(n-1))/4` (C) `(^mC_2.^nC_2)/2` (D) `^mC_2+^nC_2`

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

"^mC_1=^nC_2 , then -

The coefficient of x^4 in the expansion of (1+x+x^2+x^3)^n is (A) ^nC_4 (B) ^nC_4+^nC_2 (C) ^nC_4+^nC_2+^nC_4.^nC_2 (D) ^nC_4+^nC_2+^nC_1.^nC_2

if the straight line joining the points (3,4) and (2,-1) be parallel to the line joining the points (a,-2) and (4,-a), find the value of a.

If m parallel lines in a plane are intersected by a family of n parallel lines,the number of parallelograms that can be formed is a.(1)/(4)mn(m-1)(n-1) b.(1)/(4)mn(m-1)(n-1) c.(1)/(4)m^(2)n^(2) d.none of these

Two points (a,0) and (0,b) are joined by a straight line. Another point on this line , is (A) (3a,-2b) (B) (a^2,ab) (C) (-3a,2b) (D) (a,b)