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If the sum n.1+(n-1)+(n-2).3+.........+2.(n-1)+1.n is equal to A 1/6n(n+1)1 B 1/6n²(n+1) C 1/6n(n+1)(n+2) 1/6n(n+1)(2n+1)

If the sum n.1+(n-1)+(n-2).3+.........+2.(n-1)+1.n is equal to
A 1/6n(n+1)1
B 1/6n²(n+1)
C 1/6n(n+1)(n+2)
1/6n(n+1)(2n+1)

Grade:11

1 Answers

Arun
25758 Points
4 years ago
Dear student
 
the r th term will be r(n-r+1)
 
it is summation of r(n-r+1) where r varies from 1 to n;
 
SUM ( (n+1)r - r^2 ) = (n+1)(n)(n+1)/2 - (n)(n+1)(2n+1)/6

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