Răspuns :
x² < 39 < (x+1)² *** x² < 39 => x < 6,24....
↓
x = {0; 1; 2; 3; 4; 5; 6} fata de care
x+1= {1; 2; 3; 4; 5; 6; 7}
↓↓
x+x² = x*(x+1) = {0; 2; 6; 12; 20; 30; 42}
↓
x = {0; 1; 2; 3; 4; 5; 6} fata de care
x+1= {1; 2; 3; 4; 5; 6; 7}
↓↓
x+x² = x*(x+1) = {0; 2; 6; 12; 20; 30; 42}