Lettervormen herleiden

Herleid de lettervormen

\(-xy+3y+3xy-3y\)

\(\begin{align}-xy+3y+3xy-3y&=-1.xy+3.y+3.xy-3.y\\&=-1.xy+3.xy+3.y-3.y\\&=2xy+0y\\&=2xy\\ \end{align}\)