Eduprobe
Question:
The sum of the series 1 + 2×3 + 3×5 + 4×7 + ...
946
915
916
945
Solution:
Tr = r(2r - 1)
S = Σ2r² - Σr
S = 2.n(n+1)(2n+1)/6 - n(n+1)/2
S₁₁ = 2/6(11)(12)(23) - 1/2(11)(12) = (44)(23) - 66 = 946
946
915
916
945
Tr = r(2r - 1)
S = Σ2r² - Σr
S = 2.n(n+1)(2n+1)/6 - n(n+1)/2
S₁₁ = 2/6(11)(12)(23) - 1/2(11)(12) = (44)(23) - 66 = 946