well, now you know that
d = p-3 - (p-5) = 2
2p-15 - (p-3) = 2, so p=14
so, a = p-5 = 9
n/2 (2*9 + (n-1)*2) = 180
n = 10
The first three terms of an A.P. are p-5,p-3 and 2p-15.If the sum of the first n terms of the progression is 180,find the value of n.
Answer:n=10
2 answers
Ohh..thank u ^^