( a + 2 ) x ( b - 3 ) = 28
28 = 1 x 28 = 2 x 14 = 4 x 7 = 7 x 4 = 14 x 2 = 28 x 1
_____________________________________
a + 2 = 28 ⇒ a = 28 - 2 = 26 ∈ N
b - 3 = 1 ⇒ b = 4 ∈ N
( 26 + 2 ) x ( 4 - 3 ) = 28 x 1 = 28
_____________________________
a + 2 = 14 ⇒ a = 12 ∈ N
b - 3 = 2 ⇒ b = 5
( 12 + 2 ) x ( 5 - 3) = 14 x 2 = 28
___________________________
a + 2 = 7 ⇒ a = 7 - 2 = 5
b - 3 = 4 ⇒ b = 7
( 5 + 2 ) x ( 7 - 3 ) = 7 x 4 = 28
__________________________
a + 2 = 4 ⇒ a = 2
b - 3 = 7 ⇒ b = 10
( 2 + 2 ) x ( 10 - 3 ) = 4 x 7 = 28
__________________________
a + 2 = 2 ⇒ a = 0 ∈ N
b - 3 = 14 ⇒ b = 17
( 0 + 2 ) x ( 17 - 3 ) = 2 x 14 = 28
______________________________
a + 2 = 1 ⇒ a = - 1 ∉ N ⇒ a + 2 ≠ 1
_____________________________
Solutii: ( a; b ) = ( 0; 17 ); ( 2; 10 ); ( 5; 7 ); ( 12; 5 ); ( 26; 4)
