Question

tìm số nguyên x,y 
(x-1).(y+2)=7

 

Answer 1

\(\left(x-1\right)\left(y+2\right)=7\)

\(\Rightarrow\left[{}\begin{matrix}x-1=7\\y+2=7\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=8\\y=5\end{matrix}\right.\)

Vậy \(x=8\) , \(y=5\)

Answer 2

\(\left(x-1\right)\left(y+1\right)=\left(-1\right)\left(-7\right)=\left(-7\right)\left(-1\right)=7.1=1.7\)

TH1 : x - 1 = -1 ; y + 1 = -7 <=> x = 0 ; y = -8 

TH2 : x - 1 = -7 ; y + 1 = -1 <=> x = -6 ; y = -2 

TH3 : x - 1 = 1 ; y + 1 = 7 <=> x = 2 ; y = 6 

TH4 : x - 1 = 7 ; y + 1 = 1 <=> x = 8 ; y = 0