Question

Exercițiu 1 punctele A si C va rog

Answer 1

a)
x-1 | 6
 x ∈ N   => x-1 ∈{1,2,3,6}
x-1=1 => x=2
x-1=2 => x=3
x-1=3 => x=4
x-1=6 => x=7
A={2,3,4,7}

c)
x-1 | x+7
x ∈ Z
_________
DECI
x-1|x+7
x-1|x-1
______ -
x-1| x+7-x+1
x-1| 8
=> x-1 ∈ D8={-8,-4,-2,-1,1,2,4,8}
x-1=-8 => x=-7
x-1=-4 => x=-3
x-1=-2 => x=-1
x-1=-1 => x=0
x-1=1  => x=2
x-1=2  => x=3
x-1=4  => x=5
x-1=8  => x=9
C={-7,-3,-1,0,2,3,5,9}