a) (2x+13) = 3a 2x = 3a - 13
x-4 = 3b 2x = 6b + 8 3a - 13 = 6b + 8 3(a - 2b) = 21 a - 2b = 7
b = (a-7)/2 daca a ∈{9,11,13...} b ∈ {1,2,3....}
x ∈ {7; 10; 13; 16.....}
b) 2x + 13 = 7a 2x = 7a - 13
x-4 = 7b 2x = 14b + 8 7a -13 = 14b + 8 7(a-2b) = 21 a - 2b = 3
a = 3 + 2b daca b ∈ {1,2,3,......} ⇒ a ∈ {5,7,9......}
x ∈ {11,18,25,32....}
