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**hpe** First divide both sides of the equation by 10,000 to simplify the question. A trial and error approach works as follows: compute 1.05^1, 1.05^2, 1.05^3 and so on, until you get close to the answer. Then continue with fractions as exponents, e.g. 1.05^4.5, 1.05^4.7 and so on. On the TI-83, this is done by keying in "1.05 y^x 4.7", for example (I believe).

You might get sick and tired of this, so then look up logarithms in your textbook, and find an exercise or example that sort of looks like this problem. Try to understand how it was done, and you will be on your way.