Bài 2:
\(\Rightarrow2S=2+2^2+...+2^{101}\)
\(\Rightarrow2S-S=2+2^2+...+2^{101}-1-2-...-2^{100}\)
\(\Rightarrow S=2^{101}-1\)
Bài 3:
\(\Rightarrow2A=2+2^2+...+2^{31}\)
\(\Rightarrow2A-A=2+2^2+...+2^{31}-1-2-...-2^{30}\)
\(\Rightarrow A=2^{30}-1\)
\(\Rightarrow A+1=2^{30}\)
\(\Rightarrow2S=2+2^2+...+2^{101}\)
\(\Rightarrow2S-S=2+2^2+...+2^{101}-1-2-...-2^{100}\)
\(\Rightarrow S=2^{101}-1\)
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