Question

tim x,y∈ Z biết

xy + 3x - 7y = 21

Answer 1

x=1

y=-3

Answer 2

= 0 nha bạn

k mk nha

Answer 3

xy + 3x - 7y = 21

<=> xy + 3x - 7y - 21 = 0

<=> x(y + 3) - 7(y + 3) = 0

<=> (x - 7)(y + 3) = 0

\(\Leftrightarrow\orbr{\begin{cases}x-7=0\\y+3=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=7\\y=-3\end{cases}}}\)