Math Is Fun Forum

Jitse

Member

Registered: 2007-09-15

Posts: 6

Very simple equation with logarithms

I've got some problems with the logarithms, this is the equation:

I could do something like:

Or maybe:

But I just don't know how to get to this result:

They said something like taking 10 as exponent or so, but I really don't see it.

Thanks in advance

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Very simple equation with logarithms

You were on the right lines, but you're not quite following the laws of logs.

There's a mistake in the first step because you've combined two logs together that have different constants in front of them. You need to sort that first. Also, when you bring a constant into a log it becomes a power.

Now, 10^0=1, which means that 0 can be written as log(1).

Now that you have one log term on each side, you can cancel them out.

And now you've just got a quadratic.

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It wanted to be normal.

Jitse

Member

Registered: 2007-09-15

Posts: 6

Re: Very simple equation with logarithms

Ah yes, thanks for the explanation.