does [math]-log_ax = y \Longrightarrow a^{-y} = x[/math] or [math]\Longrightarrow -a^y = x[/math]

[math]-\log_a{x} = y \equiv \log_a{x} = -y[/math]

 

Let u = -y. Then,

 

[math]\log_a{x} = u \rightarrow a^u = x \equiv a^{-y} = x[/math]

is the answer

3 y 3

log x = 3logx if that is =y , so 10 = x

 

How do you guys make the pictureS?

 

My steps can't be shown clearly

My steps can't be shown clearly

 

Your steps don't make sense.

 

And another, very similar, justification for a^-y, (using e because I can't be bothered with the subscript, but the argument's the same)

 

-lnx = y

 

lnx^-1 = y

 

x^-1 = e^y

 

x = 1/e^y

 

x = e^-y

It won't make sense since the forum can't show its proper format.

Therefore I want to use picture like them

Use LaTeX code put between two [math] tags.

 

Take a look at the thread in general maths.

It won't make sense since the forum can't show its proper format.

Therefore I want to use picture like them

 

Either use latex, or display it using standard characters, like I did.

What's latex and how to get it?

Need I go to download it?

Take a look at the thread in general maths.

Just read the other posts, or click here.

LaTeX is like TeX (look up the latter when searching on google ). Generally it´s a tool to write texts. It´s especially usefull for scientific texts (I don´t know a single scientist that does not write his/her texts with LaTeX/TeX) because it allows quite easy implementation of mathematical formulas, including figures, making tables and generally has a lot of features to format your text or assisting you in creating a well formatted text on your own. Firgures, chapters, subsections and formulas are numbered automatically, for example so you can insert a new formula anywhere in te text and don´t have to care about increasing the numbers of the following equations. Texts tend to also look very nice (ever wondered what scientific books are written with? -> TeX). TeX compiles your raw-text into a .pdf or .ps.

You can download it for free (dunno where - beware: My distribution was about 130MB packed). Raw-texts can be written with any ascii-editor but there are specialized editors available. I use TeXnicCenter - it´s freeware and comes close to the more famous TeXEdt.

To use TeX in this forum I think you don´t have to download anything. You can simply write TeX-code between math-tags as dave said (it´s somewhere in the FAQ, i think). If you´re an ongoing scientist or want to write good-looking essays involving formulas for school it might be a good idea to get used to TeX - most love it.

I posted a LaTeX tutorial in General Math, which jordan has kindly linked to.

thank you