de abc : 11 thi a:11; b:11;c:11 hay a+b+c:11
Giai
abc:11=a+b+c
100a+10b+c=11(a+b+c)
suy ra a=1 cb=89 nen b=9 c=8
vay abc = 198
kick gium minh nhe
bai nay o thi het hoc ki1 to lam roi
abc=(a+b+c)x 11
a x 100 + b x 10 + c = a x 11 + b x 11 +c x 11
a x(89+11)+b x 10 + c= a x 11+ b x (10+1) + c x(10+1)
a x 89 +a x 11 +b x 10 +c = a x11 + b x 10 + b + c x 10 +c
a x 89 = b + c x10
NX : Vi c va b <10 nen b + c x 10 < 10+10x10
hay b + c x10< 110
suy ra: a< 2 vi neu a = 2 thi 2 x 89 > 110
vay a = 1
voi a = 1 thi 1 x 89= b + c x10
b + c x 10 = 89
xet thay 89 co chu so tan cung la 9, c x 10 co chu so tan cung la o
ma b < 10 nen b= 9
voi b=9 thi c =8
vay abc = 198