#| BEGIN (Введите свое решение) |#
(define (relative-diff x y)
  (/ (abs (- x y)) x))

(define (good-enough? guess old-guess)
  (< (relative-diff guess old-guess) 0.001))

(define (square x) (* x x))

(define (improve guess x)
  (/ (+ 
       (/ x (square guess))
       (* 2 guess))
     3))

(define (sqrt-iter old-guess x)
  (define guess (improve old-guess x))
  (if (good-enough? guess old-guess)
        guess
        (sqrt-iter (improve guess x)
                   x)));

(define (cube-root x)
  (define initial-guess 1.0)
  (if (= x 0)
    0
    (sqrt-iter initial-guess x)))
#| END |#