Answer
slope: $-1$, y-intercept: $0$.
Work Step by Step
If possible, write in the form $\quad y=mx+b$
$x+y=0$
$y= -x\qquad(+0)$
slope: $-1$, y-intercept: $0$.
Graphing when we know m and b:
Write m as a fraction, positive denominator, $m=\displaystyle \frac{\pm u}{v}.$
Start from $(0,b)$. Move v units to the right, and u units up or down, depending on the sign.
In this way you arrive at a second point, which is enough to define a line.
$m=\displaystyle \frac{-1}{1}$
$(0,0)\rightarrow(0+1,0-1)=(1,-1)$
