632.sagews

#least squares graph
x = var('x')
f(x) = 9/20 - 13/20*x - 1/4*x^2
p = plot(f,-3,4)

xPoints = [-1,0,1,2]
yPoints = [1,0,0,-2]
p1 = list_plot(zip(xPoints,yPoints),rgbcolor=(1,0,0))
(p + p1).show()