Question

[Trần Bùi Hà Trang]

Tìm \(n\in Z\) sao cho :

\(4n-5⋮2n-1\)

Answer 1

[Bùi Đức Anh]

<=>4n-5=4n-2+7

<=>2.(2n-1)+7

vì 2.(2n-1) chia hết cho 2n-1

Nên 2n-1 thuộc Ư(7)={1;7;-1;-7}

do đó 2n-1=1=>n=1

2n-1=7=>n=8

2n-1=-1=>n=0

2n-1=-7=>n=-3

Vậy n ={1;8;0;-3}

Answer 2

[uzumaki naruto]

\(\frac{4n-5}{2n-1}=\frac{4n-2}{2n-1}-\frac{3}{2n-1}\)\(=\frac{2\left(2n-1\right)}{2n-1}-\frac{3}{2n-1}\)\(=2-\frac{3}{2n-1}\)

=> \(\frac{3}{2n-1}\in Z=>\)\(3⋮\left(2n-1\right)=>2n-1\inƯ\left(3\right)\)

=> \(2n-1\in\left\{-3;-1;1;3\right\}\)

=>\(2n\in\left\{-2;0;2;4\right\}\)

=> n thuộc { -1;0;1;2}