Question

If the sum of n terms of an A.P. is $(pn+q{n}^2)$ , where p and q are constant, then common difference is

• A. q
• B. 2q
• C. p+q
• D. 2(p+q)

Answer 1

The correct option is B

2q

$S_n=pn+q{n}^2$ $a_1=S_1$ = p + q, $a_2=S_2–S_1$ = $p+3q$ therefore common difference= $a_2–a_1=2q$