# 查看完整版本 : help pls.

ahwongwongwong 2015-11-1 03:57 PM

## help pls.

Q. Solve 3^x = 3-x. This is a question from a IB math exercise. Thanks.

top11 2015-11-2 12:08 AM

What is the topic you are learning?

[url]https://www.wolframalpha.com/input/?i=3%5Ex+%3D+3-x&dataset=[/url]

You can see you cannot get an exact answer, so I need to know whether you are learning approximation.

ahwongwongwong 2015-11-2 09:51 AM

## 回覆 2# 的帖子

thanks. this is a question from topic of log, in I B mathematics text book. I can only solve it by graphical method as I was trained in HKCEE level. do you think it can be solved by numerical method? or any secret method taught in IB syllabus only? thanks again.:)

top11 2015-11-2 10:11 AM

[quote]原帖由 [i]ahwongwongwong[/i] 於 2015-11-2 09:51 AM 發表 [url=http://www.discuss.com.hk/redirect.php?goto=findpost&pid=429093276&ptid=25244080][img]http://www.discuss.com.hk/images/common/back.gif[/img][/url]
thanks. this is a question from topic of log, in I B mathematics text book. I can only solve it by graphical method as I was trained in HKCEE level. do you think it can be solved by numerical method?  ... [/quote]
Surely the answer can be "approximately solved" by numerical methods, it depends on which numerical methods you have learnt:
bisection method, secant method, Newton's method, iteration method, etc.

You can also solve that graphically as you said.
3^x = 3 - x
log(3^x) = log(3 - x)
xlog(3) = log(3 - x)
It depends on what graphs you have.

## 回覆 3# 的帖子

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