the summation of -2n - 3, from n equals 2 to 10 is the sum of the first 10 term minus the first term.
Tn = -2n - 3
T1 = -2(1) - 3 = -2 - 3 = -5
T10 = -2(10) - 3 = -20 - 3 = -23
Sn = n/2 (T1 + Tn)
S10 = 10/2 (-5 + (-23)) = 5(-5 - 23) = 5(-28) = -140
Therefore, the summation of -2n - 3, from n equals 2 to 10 = -140 - (-5) = -140 + 5 = -135.
