#| BEGIN (Write your solution here) |#
(define (cube-iter guess x)
  (if (good-enough? guess (improve guess x))
      guess
      (cube-iter (improve guess x) x)))

(define (good-enough? guess pre-guess)
  (< (abs (- guess pre-guess)) 0.00000001))

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

(define (cube-root x)
  (cube-iter 1.0 x))
#| END |#