Question

Tim n de phan so \(\frac{3n+2}{n-1}\)co gia tri la so nguyen

Answer 1

Ta co 3n+2/n-1 

         = 3(n-1) +5/ n-1

          = 3 + 5/n-1

De phan so 3n+2/n-1 co gia tri la so nguyen thi 3+5/n-1 co gia tri la so nguyen

Suy ra 5/n-1 co gia tri la so nguyen

Do do n-1 la uoc cua 5

cac uoc cua 5 la -5; -1; 1;5

Ta co bang sau:

n-1	-5	-1	1	5
n	-4	0	2	6

Vay n thuoc { -4;0;2;6}

Answer 2

huy lam bai on tap tieng anh.Ban ay lam duoc \(\frac{1}{8}\)so bai tap vao ngay thu bay va \(\frac{3}{4}\)so bai tap vao ngay chu nhat.Hoi phan so nao chi phan bai tap mon tieng anhma ban da lam duoc trong thu bay va chu nhat

Answer 3

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

Để \(\frac{3n+2}{n-1}\)có giá trị nguyên thì \(\frac{5}{n-1}\)có giá trị nguyên  mà \(n\in N\)

=>\(n-1\inƯ\left(5\right)\)

=>\(n-1\in\left\{1,5\right\}\)

=>  \(n\in\left\{2,6\right\}\)

Vậy \(n\in\left\{2,6\right\}\)

Answer 4

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