[tex]\left[\Big(-\dfrac{1}{2}\Big)\cdot \Big(-\dfrac{1}{2}\Big)^2\cdot \Big(-\dfrac{1}{2}\Big)^3\cdot ...\cdot \Big(-\dfrac{1}{2}\Big)^{100}\right] \cdot \Big(-\dfrac{1}{2}\Big)^{5050}= \\ \\ = \Big(-\dfrac{1}{2}\Big)^{1+2+3+...+100}\cdot \Big(-\dfrac{1}{2}\Big)^{5050}= \\ \\ = \Big(-\dfrac{1}{2}\Big)^{\frac{100\cdot 101}{2}}\cdot \Big(-\dfrac{1}{2}\Big)^{-5050} = \\ \\ = \Big(-\dfrac{1}{2}\Big)^{5050}\cdot \Big(-\dfrac{1}{2}\Big)^{-5050}= \Big(-\dfrac{1}{2}\Big)^{5050-5050} =[/tex]
[tex]=\Big(-\dfrac{1}{2}\Big)^{0} = 1[/tex]