Toán Lớp 6: tìm các số nguyên x, y thỏa mãn x(y-1) = y+2
Leave a reply
Register Now
Login
Lost Password
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Toán Lớp 6: tìm các số nguyên x, y thỏa mãn x(y-1) = y+2
Comments ( 2 )
Dap an duoi phan hinh anh nhe
x . ( y – 1 ) = y +2
⇒ x . ( y – 1 ) – y – 2 = 0
⇒ x . ( y – 1 ) – y – 2 + 3 = 3
⇒ x . ( y – 1 ) – ( y + 2 – 3 ) = 3
⇒ x . ( y – 1 ) – ( y – 1 ) = 3
⇒ ( x -1 ) . ( y – 1 ) = 3 = 1 . 3 = ( – 1 ) . ( – 3 )
Ta có bảng sau :
\begin{array}{|c|c|c|}\hline \text{x – 1}&\text{1}&\text{3}&\text{- 1}&\text{- 3}\\\hline \text{y – 1}&\text{3}&\text{1}&\text{- 3}&\text{- 1}\\\hline \text{x}&\text{2}&\text{4}&\text{0}&\text{- 2}\\\hline \text{y}&\text{4}&\text{2}&\text{- 2}&\text{0}\\\hline\end{array}
Vậy , ( x ; y ) ∈ { ( 2 ; 4 ) ; ( 4 ; 2 ) ; ( 0 ; – 2 ) ; ( – 2 ; 0 )