## Calculus: Early Transcendentals 8th Edition

$z=y$
Draw $f(x,y) = y$ So we know that $f(x,y)$ can also be written as $z$. So from there we now know that $z=y$. In 2D this is just a diagonal line crossing the origin. If we look at it in 3D that line becomes a plane and looks like this: