def f(x):
    return x**2-2*x+7
def coeffs_secantes(f,a,b,n):
    liste_coeffs=[]
    h=(b-a)/n
    for i in range(n):
        liste_coeffs.append(round((f(a+h*(i+1))-f(a+i*h))/h,2))
    return liste_coeffs