#| BEGIN (Write your solution here) |#
(define (square x) (* x x))
(define (average x y) 
  (/ (+ x y) 2))
(define (sqrt-iter guess x)
  (if (good-enough? guess x)
      guess
      (sqrt-iter (improve guess x) x)))
(define (improve guess x)
  (average guess (/ x guess)))
 (define (good-enough? guess x) 
   (= (improve guess x) guess)) 
(define (square-root x)
  (sqrt-iter 1.0 x))
#| END |#