; Ex 1.8

(define improve-cube-root

(lambda (x y)

(/ (+ (/ x (* y y)) (* 2 y))

3)))

(define cube-root-iter

(lambda (guess x )

(define next-guess ( / ( + (/ x (* guess guess)) (* 2 guess))

3))

(if (good-enough-2? next-guess guess)

next-guess

(cube-root-iter next-guess x))))

(define cube-root

(lambda (x)

(cube-root-iter 1.0 x)))