Question

f(x) =tan(x+4x+9x+ ... + nx)​

Answer 1

x+4x+9x+ ... + nx

$s = \frac{ \sqrt{n} ( \sqrt{n} + 1)(2 \sqrt{n} + 1)}{6}$

Then,

$f(x) = tan(\frac{ \sqrt{n} ( \sqrt{n} + 1)(2 \sqrt{n} + 1)}{6} )$