clear all
a = -20:.1:20;

for i = 1:length(a)
    c(i) = -a(i) + 2*abs(a(i));
    d(i) = sign(a(i));
    b(i) = c(i) + d(i);
    g(i) = 2*a(i)
end

% plot(a,b, 'k')
hold all
plot(a,c, 'r')
% plot(a,d, 'b')
% plot(a,g, 'y')