Graph the equation y=-x. is (5,5) on the line? what is the slope of the line?

You'll actually need to graph for the first segment
but the second part can be solved with algebra

The equation of the line is y(x)=-x

if we test the co0ordinates we can find if the point lies on the line

(5,5)
y(x)=-x

Using the x co-ordinate
y(5)= -5
y=-5

Leaving us with (5,-5)

Because (5,-5) is not (5,5)
This is not a point on the line

The slope of the line is -1 

Where’s the picture or data?