Question

Determinati cifrele a si b ,pentru care√0,a(b)+0,b(a) (tot e sub radical ) e Q .

Answer 1

0,a(b) + 0,b(a) = (10a +b - b)/90 + (10b + a - a)/90 = a/9 + b/9 = (a + b)/9
a + b = patrat perfect
a +b = 4      ( a = 1; b = 3)  √(...) = √(4/9) = 2/3
a + b = 9      ( a= 1; b = 8); ( a = 2; b = 7); (a = 3; b = 6); (a = 4; b = 5)
a + b = 16    (a= 8, b = 9)