code for piecewise expression and graphs above

> piecewise(0 < x,1,x < 0,-1,x = 0,undefined);

> plot(abs(x),x=-2..2, thickness=3,xtickmarks=[-2,-1,0,1,2],ytickmarks=[-2,-1,0,1,2],axesfont=[TIMES,BOLD,12],titlefont=[TIMES,BOLD,16],
title = `f(x) = |x|`);

> plot( piecewise(0 < x,1,x < 0,-1,x = 0,undefined),x=-2..2,title=` Graph of d/dx |x|`, discont=true,thickness=3,xtickmarks=[-2,-1,0,1,2],
ytickmarks=[-2,-1,0,1,2]);