Ta có: \(\left(2^2+1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\left(2^{32}+1\right)\)
\(=\left(2^2-1\right)\left(2^2+1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\left(2^{32}+1\right).\dfrac{1}{3}\)
\(=\left(2^4-1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\left(2^{32}+1\right).\dfrac{1}{3}\)
\(=\left(2^8-1\right)\left(2^8+1\right)\left(2^{16}+1\right)\left(2^{32}+1\right).\dfrac{1}{3}\)
\(=\left(2^{16}-1\right)\left(2^{16}+1\right)\left(2^{32}+1\right).\dfrac{1}{3}\)
\(=\left(2^{32}-1\right)\left(2^{32}+1\right).\dfrac{1}{3}=\left(2^{64}-1\right).\dfrac{1}{3}=\dfrac{2^{64}-1}{3}\)
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