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Write the following in series notation:

$$1-2x+\cfrac{4x^2}{2}-\cfrac{8x^3}{6}+\cfrac{16x^4}{24}-\cdots$$

$ \sum_{n=0}^{\infty }\cfrac{ ( -1 )^{n} ( 2x )^{n}}{n!} $

$ \sum_{n=0}^{\infty }\cfrac{ ( -1 )^{n+1} ( 2x )^{n+1}}{ ( n+1 )!} $

$ \sum_{n=1}^{\infty }\cfrac{ ( -1 )^{n} ( 2x )^{n}}{n^{2}} $

$ \sum_{n=1}^{\infty }\cfrac{ ( -1 )^{n+1} ( 2x )^{n}}{3n} $