Question

tim n thuoc N

a) 4n-5 chia het cho 2n+1                                             b) n+11 chia het cho n+1

c)7n chia het cho n-3                                                   d) n^2+n+1 chia het cho n +1   ( 2+n+1 la so mu cua n )

e)n^2 * (2n+6) chia het cho n+4                                     f) 4n+3 chia het cho 3n +1

cac ban giai tung bai cung dc nha nhung co gang giai nhanh giup mik nha chieu mik nop bai roi

Answer 1

n+11 chia het n+1

n+11=(n+1)+10

=> \(\frac{n+11}{n+1}=1+\frac{10}{\left(n+1\right)}\)

vay n+1 phai la uoc cua 10

U(10)=(1,2,5,10)

n=(0,1,4,9)

Answer 2

c) 

\(\frac{7n}{n-3}=\frac{7.\left(n-3\right)+21}{n-3}=7+\frac{21}{\left(n-3\right)}\)

vay: n-3 phai la uoc cua (21)

U(21=1,3,7,21)

n=(4,6,10,24)

Answer 3

f)

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

n+2 chia het cho 3n+1

n phai nho hon 2 

n=1 =\(\frac{\left(n+2\right)}{3n+1}=\frac{3}{4}+>\left(\right)loai\)

n=0=

 nhan

ds: n=0