4740.sagews

a = plot(-1/5*x + 18/25, (x,0,5)) 
b = point([(0,1), (1,2), (3,-1)]) 
show (a+b)

a=var('a') 
b=var('b') 
c=var('c')
f = (1-c)^2 + (2-a-b-c)^2 + (-1-9*a-3*b-c)^2 + (-25*a-5*b-c)^2
diff(f,a)

1414*a + 306*b + 70*c + 14

diff(f,b)

306*a + 70*b + 18*c + 2

diff(f,c)

70*a + 18*b + 8*c - 4

m=matrix([[1414, 306, 70], [306, 70, 18], [70, 18, 8]]) 
m

[1414 306 70] [ 306 70 18] [ 70 18 8]

w=vector([-14,-2,4])             
ans=m.solve_right(w)        
view(ans)

\newcommand{\Bold}[1]{\mathbf{#1}}\left(\frac{47}{398},\,-\frac{385}{398},\,\frac{327}{199}\right)

c= plot(47/398*x^2 -385/398*x + 327/199, (x, -10, 10))
d=point([(0,1), (1,2), (3,-1), (5,0)]) 
show(c+d)