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Dung Trần Thùy 19/03/2017 at 22:10Let \(A=\left(6+1\right)\left(6^2+1\right)...\left(6^{16}+1\right)\)
\(\Rightarrow A=\dfrac{1}{5}.5.\left(6+1\right)\left(6^2+1\right)...\left(6^{16}+1\right)\)
\(\Rightarrow A=\dfrac{1}{5}.\left(6-1\right).\left(6+1\right)\left(6^2+1\right)...\left(6^{16}+1\right)\)
\(\Rightarrow A=\dfrac{1}{5}.\left[\left(6-1\right)\left(6+1\right)\right]\left(6^2+1\right)...\left(6^{16}+1\right)\)
\(\Rightarrow A=\dfrac{1}{5}.\left(6^2-1\right)\left(6^2+1\right)\left(6^4+1\right)...\left(6^{16}+1\right)\)
\(...\)
\(\Rightarrow A=\dfrac{1}{5}.\left(6^{32}-1\right)=\dfrac{6^{32}-1}{5}\)
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FA KAKALOTS 06/02/2018 at 12:36Let A=(6+1)(62+1)...(616+1)
⇒A=15.5.(6+1)(62+1)...(616+1)
⇒A=15.(6−1).(6+1)(62+1)...(616+1)
⇒A=15.[(6−1)(6+1)](62+1)...(616+1)
⇒A=15.(62−1)(62+1)(64+1)...(616+1)
...
⇒A=15.(632−1)=632−15
