Question

Aflati nr ab stiind ca :
ab-ba este pătrat perfect .

Answer 1

ab-ba=patrat perfect

a≠0; b≠0 si a≥b

10a+b-10b-a=9a-9b=9(a-b)

9(a-b)=patrat perfect

9=3²

=> a-b=patrat perfect

a-b=0=> a=b => ab∈{11, 22, 33, …., 99}

a-b=4 => ab∈{51; 62; 73; 84; 95}