Question

tim n  thuoc z de

a) n+7 chia het n+1

b) 2n-1 chia het n-2

Answer 1

de n+7 chia het cho n+1 thi (n+1+7) chia het cho (n+1) 

vi (n+1) chia het  cho (n+1) 

nen 7chia het cho (n+1)

vay (n+1)thuoc tap hop (1;7)

suy ran thuoc tap hop (0;7)

Answer 2

a, 
    n+7     chc n+1
=>n+1+6 chc n+1
=>6         chc n+1
=>n+1=1; n+1=-1; n+1=2; n+1=-2; n+1=3; n+1=-3; n+1=6; n+1=-6
=>n=0; n=-2; n=1; n=-3; n=2; n=-4; n=5; n=-7
b,
2n-1     chc n-2
=>2n-4+5   chc n-2
=>2(n-2)+5 chc n-2
=>5            chc n-2
=>n-2=1; n-2=-1; n-2=5; n-2=-5
=>n=3; n=1; n=7; n=-3

Answer 3

Vì n + 7 chia hết cho n + 1 <=> ( n + 1 ) + 6 chia hết cho n + 1

=> 6 chia hết cho n + 1 <=> n + 1 \(\in\)Ư ( 6 )

=> Ư ( 6 ) = { +1 ; +2 ; +3 ; +6 }

=> n + 1 = +1 ; +2 ; +3 ; +6

=> n = { - 7 ; - 4 ; - 3 ; - 2 ; 0 ; 1 ; 2 ; 5 }