To find the inverse, make y the subject: 4|y|=3-x, |y|=(3-x)/4; square both sides: y^2=(3-x)^2/16. Be writing the inverse like this we are effectively saying: y=±(3-x)/4. So for each value of x there are two values for y.
When x=0, y=3/4 or -3/4, giving us two points: (0,3/4) and (0,-3/4). When x=y, x=±(3-x)/4, so 4x=3-x and y=x=3/5; or 4x=x-3 and y=x=-1, so we have (-1,-1) and (3/5,3/5).