VERY URGENT............PLS ADD THIS.........

pls sum the series........

1(2+3+4+....+n) + 2(3+4+5+..........n) + 3(4+5+6+.............n) +.............+ (n-1)n

4 Answers

62
Lokesh Verma ·

this is Σij (i<j)

1
skygirl ·

i didn get u :(

62
Lokesh Verma ·

this is (1<=i<=n-1)Σi{(n>j>i)Σj}

0<=i<j<=nΣΣij

62
Lokesh Verma ·

={ Σ(ij)-Σi2 }/2

={ {Σ(i)}2-Σi2 }/2

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