The given series is:
2×3×41+3×4×51+⋯+100×101×1021
We multiply and divide the expression by
2 to introduce this difference into the numerator:
Tn=21[(n+1)(n+2)(n+3)(n+3)−(n+1)]
Splitting this into two separate fractions reveals the telescoping structure:
Tn=21[(n+1)(n+2)(n+3)n+3−(n+1)(n+2)(n+3)n+1]
Simplifying the expression, we obtain:
Tn=21[(n+1)(n+2)1−(n+2)(n+3)1]
As we sum these terms from
n=1 to
n=99, the intermediate terms cancel out. We are left only with the first positive fraction and the last negative fraction:
S=21[2×31−101×1021]
Since
102=6×17, we find a common denominator:
S=21[101×102101×17−1]=21[101×1021717−1]=101×102858
Dividing the numerator and denominator by
6, we get:
S=101×17143
Given the form
S=101k, we identify
k=17143. Therefore, the final value is:
34k=34×17143=2×143=286