What graph represents the piecewise function?

Lower left corner

A piecewise function is basically a combination of other functions to make one single function. We can break up the given piecewise function into two parts:

f(x) = x-4

OR

f(x) = -2x

The f(x) will change depending on what x happens to be. If x is 0 or smaller, then we go with f(x) = x-4. Otherwise, if x is larger than 0, then we opt for f(x) = -2x.

To graph this, we basically graph y = x-4 and y = -2x together on the same coordinate system. We only graph y = x-4 if x is 0 or smaller. Likewise, we graph y = -2x when x > 0. This results in the graph shown in the lower left corner of your four answer choices.

Note: the closed circle means "include this point as part of the graph". The open circle means "exclude this point as part of the graph". So this is why the upper right corner is very close but not quite the answer we want.

the solution is 12x-6y