$y=1+3 x+6 x^{2}+10 x^{3}+.....\infty$ হলে $x=?$

$1-y^{-\frac{1}{3}}$

$y^{-\frac{1}{3}}-1$

$1-y^{\frac{1}{3}}$

$y^{\frac{1}{3}}-1$