Given equation: y=-x.
We need to graph the equation using line tool.
In order to graph the line, we need to find some coordinates of the graph for the given line.
We would pick some rendom numbers for x's and plug in given equation to get the values of y's for those values of x's.
Let us take x=0 first.
Plugging x=0 in y=-x, we get
y= -0 =0
We got first coordinate (0,0).
Plugging x=-1.
y= -(-1) = +1
We got second coordinate (-1,1).
Plugging x=1, we get
y = -1
We got third coordinate (1,-1).
Ploting any two of the point on the graph and picking the line tool, we can draw a straight line by joining the coordinates.