Question

11 supra 2x-3 apartine lui N

30 supra 5x -5 apartine lui N

16 supra 2x-7 apartine lui N

Answer 1

a) 11 supra (2x-3) apartine lui N
Ca impartirea sa ∈N trebuie ca 2x-3=D11
D11={-11,-1,1,11}
2x-3=-11 ∉N
2x-3=-1 ,2x=2 ,x=1
2x-3=1 ,2x=4 ,x=2
2x-3=11,2x=14 ,x=7
x={1,2,7}
b)30 /(5x -5 )apartine lui N
30/5(x-1)=6/(x-1)
x-1=D6
D6={-6,-3,-2,-1,1,2,3,6}
{-6,-3,-2} nu dau solutii in N
x-1=-1 ,x=0
x-1=1 ,x=2
x-1=2 ,x=3
x-1=3 ,x=4
x-1=6 ,x=7
x={0,2,3,4,7}

c)16 /( 2x-7) apartine lui N
2x-7=D16
D16={-16,-8,-4,-2,-1,1,2,4,8 ,16}
{-16,-8}∉N
2x-7=-4 ,2x=7-4=3∉ N
2x-7=-2 ∉ N
2x-7=-1 ,2x=6 ,x=3
2x-7=1 ,2x=8 ,x=4
2x-7=2 ∉ N
2x-7=4 ∉ N
2x-7= 8 ∉ N
2x-7= 16 ∉ N
x={3,4}