Given an A.P. whose nth term is given by an = 2 – 3n
To find the sum of the n terms of the given A.P., we use the formula,
Sn = \(\frac{n(a \,+\, l)}{2}\)
Where, a = the first term l = the last term.
Putting n = 1 in the given an, we get
a = 2 – 3(1) = -1
For the last term (l), here n = 25
a25 = 2 – 3(25) = -73
So, Sn = 25(-1 – 73)/2
= 25 x (-37)
= -925
Therefore, the sum of the 25 terms of the given A.P. is S25 = -465