bai nay hoi dai
goi abc la so co 3 chu so
goi ed la so co 2 chu so
theo de bai ta co
4xabc=5xed
gia su e va d nhan gia tri lon nha
e=9 va d=9
ta co : 5xed = 5x99 =495
suy ra 4xabc < 500 vay a phai bang 1
vi neu a >1 gia su a=2 thi 4xabc>495 (loai)
thay the vao ta co
4x1bc = 5xed
---> ed = 4/5abc
abc phai chia het cho 5 vi vay c se nhan 2 gia tri
c=0 hoac c=5
Xet truong hop c=0
ta co : 4x1b0=5xed
Phan h cau tao so
1b0 = 100 + 10b
Thay the vao : 4x(100 + 10b) =5xed
400 + 40b =5xed
chia 2 ve cho 5
ed = 80 + 8b
ed la so co 2 chũ so nen ed nhan gia tri lon nhat la 99
xet tong ed = 80 + 8b
- b= 0 ---> ed = 80
- b= 1 ---> ed = 88
- b=2---> ed = 96
- b=3 ---> ed = 104 > 99 (loai)
Ket luan truong hop C=0
ed = 80 ---> abc = 100
ed = 88---> abc = 110
ed = 96 ---> abc=120
ban tiep tuc xet truong hop c=5 tuong tu nua nha minh giai cho ban mau chot bai toan roi do bai nay co 5 dap so
nhan xet bai nay minh nghi ko ra thi vi chi danh cho thi hoc sinh gioi thoi chuc ban thanh cong
