#f(x)=-4x#

Substitute #y# for #f(x)#.

#y=-4x# is in the slope-intercept form of a linear equation #y=mx+b#, where #m# is the slope, and #b# is the y-intercept.

For #y=-4x,# #m=-4#, and #b=0#.

To find points on the line, substitute values for #x# and solve for #y#.

Determine the value of #y# if #x=0#.

#y=-4(0)=0#

So the point in which #x=0# is #(0,0)#.

To find a second point, substitute another value for #x#.

#x=1,# #y=-4#

So now we have two points, #(0,0)# and #(1,-4)#, that we can plot and then draw a straight line through the two points.

Alternatively, you can use the slope of #-4# to determine other points. You could start at the origin #(0,0)#, and move #4# places down the y-axis, then move to the right #1# place to the point #(1,-4)# Conversely, you could move #4# places up the y-axis and #1# place to the left to get the point (#-1,4)#. You can plot those points and draw a straight line through them.

graph{y=-4x [-10, 10, -5, 5]}