Polynomials related Questions by Balaji

[Balaji]

6+24+60+120+210+336+504+720 up to 10 terms is equal to ?

a) 3680


b) 4290


c) 5720


d) 6170

answer choice b


solution


=n(n+1)(n+2)
=m^3 - m


where m = n+1


sum of all = m(m+1)(m^2+m-2) 


subs m=n+1
then put n=10


=(10*11*12*13)/4
= 4290

[Balaji]

3/4+5/36+7/144+9/400......19/8100 = ?



a) 9/10



b)11/18



c)99/100



d)80/81

answer choice c

solution



t= 2n+1/n^2(n+1)^2



  =1/n^2 - 1/(n+1)^2



whic is nothing but



(1/1^2)-(1/10^2)



99/100


 

[Balaji]

1/1*4+1/2*5+1/3*6+1/4*7......1/63*66............... 



a) 9/17



b) 7/15



c) 11/18



d) 92/173

answer choice c



solution



=1/3 [(1-1/4)+(1/2-1/5)+(1/3-1/6)+...(1/63-1/66)]

=1/3*11/6

=11/18