Fie x nr. natural .
a) x + 1 / x + 6 ; dar x + 1 / x + 1 => x + 1 / ( x + 6 ) - ( x + 1 ) => x + 1 / 5 =>
x + 1 ∈ D5 => x + 1 ∈ { 1 , 5 } => x∈{ 0 , 4 } ;
b) x + 2 / 2x + 29 ; dar x + 2 / 2( x + 2 ) =>x + 2 / ( 2x + 29 ) - ( 2x + 4 ) =>
x + 2 / 25 => x + 2 ∈ { 1 , 5 , 25 } => x ∈ { 3 , 23 }
Bafta !