Giải thích các bước giải:
$(1+1)^{100}=C_{100}^0+C_{100}^1+C_{100}^2+....+C_{100}^{99}+C_{100}^{100}=2^{100}\\
(1-1)^{100}=C_{100}^0-C_{100}^1+C_{100}^2+....-C_{100}^{99}+C_{100}^{100}=0\\
\Rightarrow S_{2}= C_{100}^0+C_{100}^2+....+C_{100}^{100}=2^{99}\\
(1+i)^{100}=C_{100}^0+C_{100}^1i+C_{100}^2i^2....+C_{100}^{99}.i^{99}+C_{100}^{100}.i^{100}\\
(1-i)^{100}=C_{100}^0-C_{100}^1i+C_{100}^2i^2+....-C_{100}^{99}i^{99}+C_{100}^{100}.i^100\\
\Rightarrow S_{1}=\frac{(1+i)^{100}-(1-i)^{100}}{2}=C_{100}^1+C_{100}^2.i^2+C_{100}^4.i^4+...+C_{100}^{98}.i^{98}+C_{100}^{100}.i^{100}=C_{100}^0-C_{100}^2+C_{100}^4+...-C_{100}^{98}+C_{100}^{100}\\
S=\frac{S_{1}+S_{2}}{2}=\frac{(1+i)^{100}-(1-i)^{100}}{4}+2^{98}=2^{98}$
