Ta có: \(A=\left(2+1\right)\left(2^2+1\right)\left(2^4+1\right)...\left(2^{64}+1\right)\)
\(A=\left(2^2-1\right)\left(2^2+1\right)\left(2^4+1\right)...\left(2^{64}+1\right)\)
\(A=\left(2^4-1\right)\left(2^4+1\right)...\left(2^{64}+1\right)\)
\(A=\left(2^{16}-1\right)...\left(2^{64}+1\right)\)
\(A=2^{64}-1\)
Ta thấy \(2^{64}-1< 2^{64}\)
Vậy \(A< B\)
Chúc bạn học tốt!