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Exponents
Properties of Exponents
A quantity with an exponent has three components--the
base, the
exponent,
and the coefficient.
- In the quantity 3x5, the coefficient is 3, the base is x, and
the exponent is 5.
- In the quantity 3(16)7x, the coefficient is 3, the base is
16, and the exponent is 7x.
- In the quantity 26(2y)xy, the coefficient is 16, the base is 2y,
and the exponent is xy.
- In the quantity r2, the (implied) coefficient is 1, the base is
r, and the exponent is 2.
Adding and Subtracting Quantities with Exponents
We cannot simplify by grouping two terms together unless they have the
same base and the same exponent. For example, we
cannot combine terms in expressions such as 52 +122 or 53 +54. We can, however, simplify 45 +45 and 2x2 +5x2. To
group two terms with the same base and the same exponent, add their
coefficients. Thus, 45 +45 = 1(4)5 + 1(4)5 = (1 + 1)(4)5 = 2(4)5 and 2x2 +5x2 = (2 + 5)x2 = 7x2.
Multiplying Quantities with Exponents
We can multiply two quantities with exponents if they have the same
base. To multiply two quantities with the same base, multiply their
coefficients and add their exponents. For example, 4(5)5×3(5)2 = (3×4)(5)5+2 = 12(5)7 and 5(2x)2×6(2x)y = (5×6)(2x)2+y = 30(2x)2+y.
Dividing Quantities with Exponents
Distributive Property of Exponents
If an exponent acts on single term in parentheses, we can
distribute the exponent over the term. For example, (2×5)2 = (22)(52), (3x)6 = 36x6, and 3(4xy)5 = 3(45)x5y5.
Be careful! If an exponent acts on multiple terms in
parentheses (i.e. if there is a "+" or "-" sign in the parentheses),
it cannot be distributed: (5 + 3)2≠52 +32 and (4a + b)2≠a2 + b2.
Taking a Power of a Power
Sometimes, the base will include an exponent, like in the expression
(22)3. If this is the case, multiply the exponent in the base by
the exponent which acts on the base: (22)3 = 22×3 = 26
and (x5)y = x5×y = x5y.
Writing Quantities with a Common Base
We cannot multiply quantities if they do not have the same base. However, we can often
use the "power of a power" rule to write two quantities as quantities with a common base.
If the two bases are powers of a common base (for example, 4 and 32 are both powers of
2), rewrite each base as a power of the common base. Then uses the power of a power
rule to combine the exponents of each base. Finally, use the multiplication rule and add
the exponents.
Example: 95×274 =?
95 = (32)5 = 310; 274 = (33)4 = 312
95×274 = 310×312 = 310+12 = 322.
Summary of Properties
Addition: cxa + dxa = (c + d )xa
Subtraction: cxa - dxa = (c - d )xa
Multiplication: cxa×dxb = (cd )xa+b
Division: = ( )xa-b
Distribution: (cd )a = cada
Power of a Power: c(xa)b = cxab
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