Răspuns:
Ab+ba=patrat perfect
10a+b+10b+a=patrat perfect
11a+11b=patrat perfect
11(a+b)=patrat perfect
a+b=patrat perfect : 11
singurul patrat perfect care se imparte la 11 este 121=11 la patrat
a+b=121:11
a+b=11
a,bdiferit de 0, 10
a, b apartin de multimea(2 3 4 5 6 7 8 9)
abonare?