Question

[FC Khởi My]

Cho n thuoc N, chung to cac phan so sau la toi gian : 

a,    2n+1/5n+2

b,    5n+2/3n+1

c,    5n+2/(3n+1).(2n+1)

Answer 1

[Wall HaiAnh]

a, gọi d là ƯCLN(2n+1, 5n+2 )

\(\Rightarrow\hept{\begin{cases}2n+1⋮d\\5n+2⋮d\end{cases}}\Rightarrow\hept{\begin{cases}5\left(2n+1\right)⋮d\\2\left(5n+2\right)⋮d\end{cases}}\Rightarrow\hept{\begin{cases}10n+5⋮d\\10+4⋮d\end{cases}}\)

\(\Rightarrow\left(10+5\right)-\left(10+4\right)⋮d\)

\(\Rightarrow10+5-10-4⋮d\)

\(\Rightarrow1⋮d\)

\(\Rightarrow d=\left\{-1;1\right\}\)

vậy...............

Answer 2

[FC Khởi My]

Còn phần b và phần c thì sao???