i got confused.need guide.

x(t)= u(t-1)+(t-1)u(t-1)-2(t-2)u(t-2)+(t-4)u(t-4)-u(t-4)

it is in unit step, so i convert it to sum of singularity functions.
then i get this

x(t)= u(t-1)+r(t-1)-2r(t-2)+r(t-4)-u(t-4)

then i have to sketch the graph but i don't know how to do when it comes to -2r(t-2). should i separate it to become -r(t-2)-r(t-2)??

 

Please define r(t).