% parametric line from equation a=2; b=-4; c=-9; x = [-10 10]; y = -(c+a*x)/b; plot(x,y,'k--'); grid on p0 = -(c/(a^2+b^2))*[a b]; k = [b -a]; p = [p0-k*0.5; p0+k*0.5]; hold on plot(p(:,1),p(:,2),'b'); plot(p0(1),p0(2),'rx','MarkerSize',9,'LineWidth',2); plot(0,0,'ko'); hold off axis equal
