Question

va rog ajutati-ma la acest ex ...

Answer 1

A = {x∈Z I 12/(x+1) ∈Z}

12/(x+1) ∈ Z <=> (x+1) = 12 , -12 , 6 ,-6 , 4 ,-4 , 3 -3 , 2 , -2 , 1 , -1

=> x = { 11 ; -13 ; 5 ; -7 ; 3 ; -5 ; 2 ; -4 ; 1 ; -1 ; 0 ; -2}

B = {x∈Z I -20/(2x+3) ∈N}

-20/(2x+3) ∈N  <=> (2x-3) = -20 ; -10 ; -5 ; -4 ; -2 ; -1

2x-3 = -20 => x = -17/2 ∉Z

2x-3 = -10 => x =-7/2 ∉Z

2x-3 = -5 => x = -2/2 = -1∈Z

2x-3 = -4 ; -2 => x∉Z

2x-3 = -1 => x = 2/2 = 1∈Z

=> x= {-1 ; 1}

C = {(x,y) ∈ZxZ I xy =-8}

xy =-8  <=> x = -8 si y = 1  ; x = -4 si y = 2 ; x = -2 si y = 4 ; x = -1 si y = 8

                 y = -8 si x = 1  ; y = -4 si x = 2 ; y = -2 si x = 4 ; y = -1 si x = 8

D = {x∈Z I 4≤IxI≤8}  => x = {4;5;6;7;8;-4;-5;-6;-7;-8}