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Number Systems - Laws of Exponents for Real Numbers

Grade 9CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

Definition of Exponents: For any real number aa and a positive integer nn, the expression ana^n represents the product of aa multiplied by itself nn times. Visually, the base aa is written as a standard-sized number, while the exponent nn is written as a smaller superscript at the top right corner.

Product Law: When multiplying powers with the same base, you keep the base and add the exponents (aman=am+na^m \cdot a^n = a^{m+n}). This visualizes as merging two groups of identical factors into one single group containing all factors.

Quotient Law: When dividing powers with the same base, you keep the base and subtract the exponent of the denominator from the exponent of the numerator (aman=amn\frac{a^m}{a^n} = a^{m-n}). This represents the process of 'canceling out' matching factors from the top and bottom of a fraction.

Power of a Power Law: When a power is raised to another power, the exponents are multiplied together ((am)n=amn(a^m)^n = a^{mn}). Visually, this represents a block of aa factors repeated nn times, resulting in a single base with a larger product exponent.

Power of a Product and Quotient: An exponent outside a bracket containing a product or quotient applies to every individual term inside the bracket. For example, (ab)n=anbn(ab)^n = a^n b^n and (ab)n=anbn(\frac{a}{b})^n = \frac{a^n}{b^n}. This acts like a distributive property for exponents over multiplication and division.

Zero and Negative Exponents: Any non-zero real number raised to the power of 0 is always 1 (a0=1a^0 = 1). A negative exponent indicates a reciprocal; ana^{-n} moves the base to the denominator with a positive exponent (an=1ana^{-n} = \frac{1}{a^n}).

Rational Exponents: For a real number a>0a > 0 and integers mm and nn, amna^{\frac{m}{n}} represents the nthn^{th} root of aa raised to the mthm^{th} power. Visually, the denominator of the fraction sits inside the notch of the radical sign amn\sqrt[n]{a^m}.

📐Formulae

aman=am+na^m \cdot a^n = a^{m+n}

aman=amn\frac{a^m}{a^n} = a^{m-n}

(am)n=amn(a^m)^n = a^{mn}

(ab)n=anbn(ab)^n = a^n b^n

(ab)n=anbn(\frac{a}{b})^n = \frac{a^n}{b^n}

a0=1a^0 = 1 (where a0a \neq 0)

an=1ana^{-n} = \frac{1}{a^n}

amn=(an)m=amna^{\frac{m}{n}} = (\sqrt[n]{a})^m = \sqrt[n]{a^m}

💡Examples

Problem 1:

Simplify: 6412(2223)64^{\frac{1}{2}} \cdot (2^2 \cdot 2^3)

Solution:

Step 1: Simplify the square root part. Since 64=8264 = 8^2, we have 6412=(82)12=82×12=81=864^{\frac{1}{2}} = (8^2)^{\frac{1}{2}} = 8^{2 \times \frac{1}{2}} = 8^1 = 8.\Step 2: Simplify the second part using the Product Law. 2223=22+3=252^2 \cdot 2^3 = 2^{2+3} = 2^5.\Step 3: Calculate 252^5. 25=322^5 = 32.\Step 4: Multiply the results. 8×32=2568 \times 32 = 256.

Explanation:

We first converted the rational exponent into a root/power, then used the Product Law of exponents to combine terms with base 2, and finally calculated the product.

Problem 2:

Simplify and write the answer with a positive exponent: 23122314\frac{23^{\frac{1}{2}}}{23^{\frac{1}{4}}}

Solution:

Step 1: Use the Quotient Law for exponents with the same base (a=23a = 23).\Step 2: Subtract the exponents: 23121423^{\frac{1}{2} - \frac{1}{4}}.\Step 3: To subtract the fractions, find a common denominator (4): 1214=2414=14\frac{1}{2} - \frac{1}{4} = \frac{2}{4} - \frac{1}{4} = \frac{1}{4}.\Step 4: The result is 231423^{\frac{1}{4}}.

Explanation:

Since the bases are identical, we subtract the power in the denominator from the power in the numerator using the law aman=amn\frac{a^m}{a^n} = a^{m-n}.