\(3x^2-\left(5y-1\right)x-2y^2-2y-7=0\)
\(\Delta=\left(5y-1\right)^2+12\left(2y^2+2y+7\right)\)
\(=49y^2+14y+85=\left(7y+1\right)^2+84\)
Để x;y nguyên \(\Rightarrow\left(7y+1\right)^2+84=k^2\)
\(\Rightarrow k^2-\left(7y+1\right)^2=84\Leftrightarrow\left(k-7y-1\right)\left(k+7y+1\right)=84\)
\(\Rightarrow...\)