(define (root number degree tolerance)
  (define (good-enough? next guess)
    (< (abs (- next guess)) tolerance))
  (define (improve guess)
    (/ (+ (* (- degree 1) guess) (/ number (expt guess (- degree 1)))) degree))
  (define (*root guess)
    (let ((next (improve guess)))
      (if (good-enough? next guess)
          guess
          (*root next))))
  (*root 1.0))

(display (root (expt 2 10) 10 0.1))
(newline)
(display (root (expt 2 10) 10 0.01))
(newline)
(display (root (expt 2 10) 10 0.001))
(newline)