x=var('x')
x0=var('x0')
h=var('h')
m=var('m')
N=var('N')
f = lambda x: x^3+2*x-1
x0=1
h=1
N=10
R=[]
for n in range(1,N):
R.append(plot(n*(f(x0+1/n)-f(x0))*(x-x0)+f(x0), rgbcolor=(0.5,1/n,1/n),xmin=0,xmax=4)+plot(f,rgbcolor=(0,1,0.2),xmin=0,xmax=4))
aR=animate(R,xmin=0.9,xmax=2.1,ymin=1.9,ymax=11.1)
aR.show()