Question

chứng minh các phân số sau tối giản vs mọi số tự nhiên n :

a) 2n+1/4n+5

b)3n+1/n+4

Answer 1

a) Gọi \(d=ƯCLN\left(2n+1;4n+5\right)\)

\(\Leftrightarrow\hept{\begin{cases}2n+1⋮d\\4n+5⋮d\end{cases}}\)

\(\Leftrightarrow\hept{\begin{cases}4n+2⋮d\\4n+5⋮d\end{cases}}\)

\(\Leftrightarrow3⋮d\)

Vì \(d\in N;3⋮d\Leftrightarrow d=1;3\)

Ok đề sai!

Answer 2

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