Question

tìm ab biet, ab + a+b =63

Answer 1

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