ab + A +B = 63
=> so ab ≤ 63, nen a+b ≤ 6+3 hay a+b ≤ 9
vi a+b ≤ 9 nen => A=B (1)
Theo de bai ta co A = a+b (2)
Thay (1) va (2) vao de bai, ta co:
ab +2(a+b) = 63 10a + b + 2a + 2b = 63
4a + b = 21b = (21 - 4a)
Vi a,b la chu so, nen 0≤a,b≤ 9, hay 0≤21-4a ≤9 => a=3;4;5
Neu a=3 => b=9 => loai (vi a+b =12>9)
Neu a=4 => b=5 (chon)
Neu a=5 => b=1 (chon)
Vay so can tim la 45 hoac 51