[tex] - 4y = v - 4x \\ y = \frac{ - v}{4} + x[/tex]
[tex]\\ \rm\dashrightarrow V=-4y+4x[/tex]
[tex]\\ \rm\dashrightarrow -4y=V-4x[/tex]
[tex]\\ \rm\dashrightarrow y=\dfrac{V-4x}{-4}[/tex]
[tex]\\ \rm\dashrightarrow y=x-\dfrac{V}{4}[/tex]
