Question

Find the number a and b with ab+ba is số chính phương

Answer 1

(2,9) , (3,8) , (4,7) , (5,6)

Explanation:

ab+ba = 10a+b+10b+a = 11a+11b = 11(a+b)

if a+b = 11 then ab+ba = 11²

(a,b) or (b,a) : (2,9) , (3,8) , (4,7) , (5,6)

check: 29+92 = 121 = 11²

56+65 = 121 = 11²