function secant_method(f::Function, x0::T, x1::T, tol::AbstractFloat, n::T) where {T}
f0 = f(x0)
f1 = f(x1)
for i in 1:n
x = x1 - f1*(x1 - x0)/(f1 - f0)
fx = f(x)
x0 = x1
x1 = x
f0 = f1
f1 = fx
if abs(x1 - x0) < tol
return x1
end
end
return nothing
end