(define (sqrt x)
	(sqrt-iter 1.0 10000.0 x))
(define (sqrt-iter guess lastguess x)
	(if (good-enough? guess lastguess)
	    guess
	    (sqrt-iter (improve guess x)
			guess
			x)))
(define (improve guess x)
	(average guess (/ x guess)))
(define (average x y)
	(/ (+ x y) 2.0))
(define (good-enough? guess lastguess)
	(< (abs (- guess lastguess)) 0.001))