Question

ab( cu bara deasupra) =?
ab( '' '' '' ) - ba( cu bara) =a (b-1)
a diferit de b
a, b prime intre ele.

Answer 1

ab-ba=10a+b-10b-a=a(b-1`)

9a-9b=ab-a

10a-9b=ab

10a-ab=9b

a(10-b)=9b

a=9*(b)/(10-b) ∈N

b cifra, b∈{1;2...9}

si b≤10-b pt ca a≤9

deci 2b≤10, deci b≤5

a=9*(b)/(10-b)

b=1, a=1 nu are sens sa se puna probleam prime intre ele, dar severifiac relatia

11-11=1*(1-1)

b=2, a=9*2/8=9/4∉N

b=3, a=9*3/7∉N

b=4, a=9*4/(10-4)=9*4/6=36/6=6∈n , dar 4 si 6 nu sunt prime intre ele. au cmmdc=2

b=5, a=9*5/5=9

Verificare ;95-59=36=9*(5-1)=9*4. bine rezolvat

Extra;

data al Ev Nat, cl8, acum vreo 7 ani...

verificare94-49=45=