# [racket] HTDP 2nd edition exercise 4.2.3 - floating point issues

;; equation3 : number -> boolean
;; to determine whether n is a solution for 2n^2 = 102
(define (equation3 n)
(=~ (* 2 n n) 102 .001))
-- Matthias
On Oct 22, 2013, at 8:40 AM, Bo Gus <forumangus at gmail.com> wrote:
>* equation 2 is 2n^2 = 102 so I implement like this:
*>*
*>* ;; equation3 : number -> boolean
*>* ;; to determine whether n is a solution for 2n^2 = 102
*>* (define (equation3 n)
*>* (= (* 2 n n) 102))
*>*
*>* And my answer is the same as per the online answer. so great.
*>*
*>* But how can I check a valid answer.
*>*
*>* Eg if I do:
*>*
*>* (equation3 (sqrt 51))
*>* >false
*>*
*>* same using - square root 51.
*>*
*>* How can I fix this? Is the only way to do a range check? Eg have some sort of tolerance - eg between 0.01 above and below answer? Any other ideas?
*>*
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