Question

If sum of (n+1) terms of an arithmetic sequence is pn^2+qn+r, prove that p+r=q

Answer 1

Here n+1=0
n=-1
$pn ^{2} + qn + r$
Put the value of n in above equation,

p(-1)^2 + q(-1) + r = 0
p - q + r = 0
p + r = q