$y=2 x-3 x^{2}+4 x^{3}-5 x^{4}+\ldots .$ হলে, $(1+x)=$ কত?

$(1+y)^{-\frac{1}{2}}$

$(1-y)^{-\frac{1}{2}}$

$(1+y)^{-1}$

$(1-y)^{-1}$