var('x')
y1=1/2-1/2*x
y2=x+2
p3=point((-1,1),size=60, color='green')
p1=plot(y1, (x, -2, 2), gridlines=True, axes_labels=['$x$','$y$'], fontsize=14, color='blue')
p2=plot(y2, (x, -2, 2), gridlines=True, axes_labels=['$x$','$y$'], fontsize=14, color='red')
show(p3+p1+p2)