Question

find the sum of first 10 terms for the series 1×2 + 2×3 + 3×4 + 4×5 ​

Answer 1

Answer:

sum=440

Step-by-step explanation:

1×2 + 2×3 + 3×4 + 4×5 ​

nth term of series

=n(n+1)

=n²+n

Sum of n terms

=∑n²+ ∑n

=n(n+1)(2n+1)/6 +n(n+1)/2

Putting n=10

sum=10*11*21/6+10*11/2

=385+55

=440

Answer 2

Answer:

To find : Sum of first 10 terms of AP.

Solution : 1×2+2×3+3×4+4×5+5×6+6×7+7×8+8×9+9×10+10×11

= 2+6+12+20+30+42+56+72+90+110

=440