Help With Using Exponents in Algebra

By Amy Harris
Only terms with matching variables and exponents can be added.
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Learning to use exponents in algebra can at first seem daunting, but becoming familiar with the main types of problems and adhering to a few simple rules will help you to master this math concept. A unit on exponents is almost always part of a first-year algebra course and is often taught toward the middle or end of the course. Prior to using exponents in algebra, you need to understand the principles of algebra as well as the arithmetic concept of exponents.

The Basics

In addition to possessing the relevant algebraic and arithmetic background knowledge, you must also get acquainted with some general guidelines before attempting to perform operations with exponents. Any variable raised to the zero power simplifies to 1, and any variable without an exponent displayed is assumed to have an exponent of 1. Algebraically, these laws are represented by x^0 = 1 and x^1 = x. It is also essential to know that you cannot add, subtract, multiply or divide exponents whose bases differ from one another. For example, r^3 + q^4 and m^7/j^7 cannot be simplified further. And, when writing solutions that involve multiple variables, order doesn’t matter. For instance, (t^4)(s^3) and (s^3)(t^4) are equivalent.

Adding and Subtracting

If adding or subtracting exponents, add or subtract only the coefficients, leaving the exponents and variables unchanged. Consider the expression 5x^7 – 2x^7. To simplify this, subtract two from five, resulting in 3x^7. Keep in mind, however, that you cannot add or subtract terms whose exponents do not match. In such situations, terms cannot be combined; they must be left as-is. For instance, suppose that you are asked to simplify x^2 + x^3. Many people assume that the answer would be x^5. But the correct answer is x^2 + x^3.

Multiplying

When multiplying powers that have the same base, add the exponents. Consider -6y^4 * 2y^5. Multiply the coefficients, -6 and 2, to get -12, and then add the exponents, producing y^9. In total, this expression simplifies to -12y^9. If an expression contains multiple bases, multiply like bases by one another. For example, multiplying 5f^3n^2f^4n results in 5(f^7)(n^3).

Dividing

When dividing powers that share the same base, subtract the exponent in the denominator from the exponent in the numerator. (See Reference 5) Consider 8x^9/4x^3. Divide the coefficients, 8 and 4, resulting in 2. Subtract the exponents, 9 and 3, resulting in x^6. This produces a solution of 2x^6. If the coefficient in the numerator is larger than the coefficient in the numerator, the answer will be a fraction or decimal. For instance, simplifying 18y^6/24y^2 yields 3y^4/4 or 0.75y^4.

Powers of Powers

Sometimes you might encounter a problem in which an exponent lies outside a set of parentheses. In these types of problems, simply multiply the exponents, and if there are any coefficients, raise them to the power of the exponent listed outside of the parentheses. For example, (3h^5)^2 simplifies to 9h^10, because the squaring the coefficient produces nine and multiplying the exponents equals 10.

Negatives

As with coefficients, exponents can also be negative. You can make a negative exponent positive by turning it into a fraction. Place the coefficient in the numerator of the fraction and the variable and its exponent in the denominator. For instance, 5x^-9 becomes 5/x^9.

About the Author

Based in western New York, Amy Harris began writing for Demand Media and Great Lakes Brewing News in 2010. Harris holds a Bachelor of Science in Mathematics from Penn State University; she taught high school math for several years and has also worked in the field of instructional design.