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Q&A #9409

Teachers' Lounge Discussion: Solving algebraic equations

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From: RON <rselby@cinci.rr.com>
To: Teacher2Teacher Public Discussion
Date: 2003061021:28:30
Subject: Re: how do I solve this problem

First of all, there is nothing to solve in your problem. You have
simply written a mathematical expression. If your intention was to
write an equation, I will work from there.

Let (1 + r/100)^12 = A  where A is some number

The idea best used here is to write down what was done to the unknown,
r.

1) divide by 100

2) add 1

3) twelfth power

To solve, simply "undo" what was done.
This needs to be done in reverse order to get back to r.

Follow the steps:

Start with the value for A.

1) take the twelfth root ( on a calculator this means raising to the
power of 1/12. Try the y^x button and make sure to put parentheses
around the 1/12.)

2) subtract 1

3) multiply by 100

This method is very basic when solving an equation for an unknown
which only appears only once. It makes use of the fact that inverse
operations "undo" each other. (i.e. roots undo powers, subtraction
undoes addition, multiplication undoes division, etc.)

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