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Topic: RE: Exponents: getting the value of x.
Replies: 0

 Cindy Ravitsky Posts: 10 Registered: 12/6/04
RE: Exponents: getting the value of x.
Posted: Sep 11, 2007 2:52 PM

For exponential equations such as these, you can solve for x by taking
the log (common or natural) of both sides, then using a property of
logarithms to get the x out of the exponent. For example:

2^x = 16

log 2^x = log 16

x log 2 = log 16

x = log 2 / log 16

If you punch this into a calculator, it gives you 4.

This same technique can be used on 2^x = 15 to get

X = log 15/ log 2

X = 3.9069 (approximately)

This of course, requires use of a calculator or log tables.

Cindy

-----Original Message-----
From: numeracy-approval@world.std.com
[mailto:numeracy-approval@world.std.com] On Behalf Of Ed Wall
Sent: Saturday, September 08, 2007 6:48 PM
To: numeracy@europe.std.com
Subject: Re: Exponents: getting the value of x.

An interesting question. A comparable question, in a sense, is how do
you get x in 2 times x = 8 without using a calculator. A, perhaps,
more interesting question is how do you get x in

2^x = 15

without a calculator?

Ed Wall

>2^4 = 16
>
>now
>
>2^x = 16
>
>we all know that x = 4. But how exactly do we get x without using a
>calculator?
>
>
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