[31 th BCS Preliminary : 2011]
1. { x(x+1)(2x+1)}/6
2. x(x+1)/2
3. x
4. {x(x+1)/2}^2
1. 2/11
2. 3/11
3. 2/13
4. 4/15
1. 250
2. 100
3. 200
4. 300
1. 36
2. 37
3. 39
4. 40
1. (0,0)
2. (4,-3)
3. (-4,3)
4. (10,10)