Câu hỏi của Nguyen Vu trong hieu

Question

Tim so tu nhien x biet :

a) 10 chia het cho n

b) 12 chia het cho n - 1

c) 20 chia het cho 2.n + 1

d) n + 5 chia het cho n + 1

e) n+7 chia het cho n + 2

f) 2.n +...

❤ Hoa ❤ · Accepted Answer

$a,10⋮n\Rightarrow n\inƯ\left(10\right)=\left\{\pm1;\pm2;\pm5\pm10\right\}.$

$\Rightarrow n\in\left\{\pm1;\pm2;\pm5;\pm10\right\}$

$b,12⋮n-1\Rightarrow n-1\inƯ\left(12\right)\left\{\pm1;\pm2;\pm3\pm4;\pm6;\pm12\right\}$

Câu trả lời:

$a,10⋮n\Rightarrow n\inƯ\left(10\right)=\left\{\pm1;\pm2;\pm5\pm10\right\}.$

$\Rightarrow n\in\left\{\pm1;\pm2;\pm5;\pm10\right\}$

$b,12⋮n-1\Rightarrow n-1\inƯ\left(12\right)\left\{\pm1;\pm2;\pm3\pm4;\pm6;\pm12\right\}$

❤ Hoa ❤ · Answer

$d,n+5⋮n+1\Rightarrow n+1+4⋮n+1.$

mà $n+1⋮n+1\Rightarrow4⋮n+1$

$\Rightarrow n+1\inƯ\left(4\right)=\left\{\pm1;\pm2;\pm4\right\}$

n+1 = 1 => n = 0

n + 1 = -1 => -2

..... tương tự vs 2; -2 ; 4 ; -4

$e,n+7⋮n+2\Rightarrow n+2+5⋮n+2$

mà $n+2⋮n+2\Rightarrow5⋮n+2$

$\Rightarrow n+2\inƯ\left(5\right)=\left\{\pm1;\pm5\right\}$

n+2 = 1 => n = -1

n + 2 = -1 => n = 3

.... tương tự vs 5 và -5

$f,2n+5⋮2n+1\Rightarrow2n+1+4⋮2n+1$

$\Rightarrow2n+1⋮2n+1\Rightarrow4⋮2n+1$

$\Rightarrow2n+1\inƯ\left(4\right)=\left\{\pm1;\pm2;\pm4\right\}$

...... tự lm