Simplifying Expressions Using Exponent Laws.
Date: 02/08/98 at 13:32:54 From: Luke Bartley Subject: Simplifying expressions using exponent laws To start off, I am having much difficulty with these types of questions. One example is: (Simplify) 5 to the exponent -4/3 divided by 5 to the exponent 2/3 The answer that was given to me was 1/25. I was 2 steps into the question when I started having trouble. How do I solve this question?
Date: 02/25/98 at 09:47:28 From: Doctor Sonya Subject: Re: Simplifying expressions using exponent laws Hi Luke, Simplifying exponential expressions like the one above is hard, but it gets easier with practice, I promise. I'll help you work through your example in two different ways. You wrote, "5 to the exponent -4/3 divided by 5 to the exponent 2/3." I'm going to write it as: 5^(-4/3) / 5^(2/3) (5^n means "5 to the nth power") The first thing to take care of are the negative exponents. You probably already know the general rule: a^(-x) = 1/a^x. For example, 4^(-2) = 1/4^2 = 1/16 3^(-3) = 1/3^3 = 1/127 Therefore you can rewrite your problem as: 1/5^(4/3) --------- 5^(2/3) You can simplify this compound fraction to: 1 ----------------- 5^(4/3) * 5^(2/3) The * means multiply. Make sure you are clear on how I did this step. Now you can multiply the two terms in the denominator together. Since they are both "5 to the something", all you have to do is add the exponents. When you do this, you'll get: 1 ----------- 5^(4/3+2/3) When I add the exponents together, I get: 1 --- 5^2 There is another rule of exponents that can also help solve this problem. Remember that: x^a/x^b = x^(a-b) What this says is that when you divide, you subtract the exponents. It's the opposite of multiplication, where you add the exponents. In our example, we had: 5^(-4/3) / 5^(2/3) So if I follow the rule above, I'll get that it is equal to: 5^(-4/3 - 2/3) Simplifying this expression gives me: 5^(-6/3) = 5^(-2) In general, when you do these types of problems, keep the rules for adding, subtracting, multiplying, and dividing in mind (or next to you on a piece of paper) and see if you can apply any of them. They will almost always allow you to simplify. -Doctors Sonya and Fox, The Math Forum Check out our web site http://mathforum.org/dr.math/
Search the Dr. Math Library:
Ask Dr. MathTM
© 1994- The Math Forum at NCTM. All rights reserved.