Unit 1 - Algebra (Real Numbers)
Lesson 5 : Laws of Exponents in Real Numbers - Notes
1. Repeated multiplication
aⁿ = the product of the real number a multiplied by itself n times.
- a = base (the repeated factor) , n = exponent (number of times the base is repeated).
- $\sqrt{3}$ $\times$ $\sqrt{3}$ $\times$ $\sqrt{3}$ $\times$ $\sqrt{3}$ = ($\sqrt{3}$)⁴ — read "$\sqrt{3}$ raised to the power of 4".
Sign rule :
- (-a)ⁿ = aⁿ if n is EVEN. Example : (-$\sqrt{5}$)⁴ = ($\sqrt{5}$)⁴ = 25.
- (-a)ⁿ = -aⁿ if n is ODD. Example : (-$\sqrt{5}$)³ = -($\sqrt{5}$)³ = -5$\sqrt{5}$.
2. Zero exponent
Any real number (not equal to zero) raised to the power 0 equals 1 :
- a⁰ = 1 (a $\neq$ 0). Examples : 3⁰ = 1 , ($\sqrt{7}$)⁰ = 1 , (-2$\sqrt[3]{4}$)⁰ = 1.
3. Negative exponent
If a $\neq$ 0 and n is a positive integer :
- a⁻ⁿ = 1/aⁿ and aⁿ = 1/a⁻ⁿ
- Examples : 5⁻² = 1/25 ; 1/3⁻² = 9 ; ($\sqrt{7}$)⁻² = 1/7 ; ($\sqrt{2}$)⁻³ = ($\sqrt{2}$)³ = 2$\sqrt{2}$.
4. The LAWS of exponents (m , n integers, bases $\neq$ 0, avoid 0⁰)
| Law | Example | Explanation |
|---|---|---|
| aᵐ $\times$ aⁿ = aᵐ⁺ⁿ | 4³ $\times$ 4² = 4⁵ | Keep the base, ADD the exponents. |
| aᵐ ÷ aⁿ = aᵐ⁻ⁿ | 3⁶ ÷ 3² = 3⁴ | Keep the base, SUBTRACT the exponents. |
| (ab)ⁿ = aⁿ bⁿ | (3 $\times$ 4)² = 3² $\times$ 4² | Power of a product = product of powers. |
| (a/b)ⁿ = aⁿ / bⁿ | (2/5)³ = 2³/5³ | Power of a quotient = quotient of powers. |
| a⁰ = 1 | ($\sqrt{3}$)⁰ = 1 | Any non-zero base to power 0 = 1. |
| a⁻ⁿ = 1/aⁿ | 3⁻² = 1/9 | Negative exponent = reciprocal with positive exponent. |
5. Powers of 10 (standard form help)
- 10 = 10¹ , 100 = 10² , 1000 = 10³
- 0.1 = 10⁻¹ , 0.01 = 10⁻² , 0.001 = 10⁻³
6. Combining radicals with exponent laws
Everything works with bases like $\sqrt{2}$ , $\sqrt{3}$ , $\sqrt[3]{4}$ , etc. Example :
- ($\sqrt{2}$)² $\times$ ($\sqrt{2}$)⁴ = ($\sqrt{2}$)⁶ = 8
- ($\sqrt{7}$)⁵ $\times$ ($\sqrt{7}$)⁻² $\times$ ($\sqrt{7}$)⁻¹ = ($\sqrt{7}$)² = 7
- ($\sqrt{5}$)⁻⁴ ÷ ($\sqrt{5}$)⁻⁶ = ($\sqrt{5}$)² = 5
7. WORKED EXAMPLES
Example 1 : Simplify (x³ $\times$ x⁻² $\times$ x⁻¹).
- x³ $\times$ x⁻² $\times$ x⁻¹ = x³⁻²⁻¹ = x⁰ = 1.
Example 2 : Simplify ($\sqrt{3}$)⁴ $\times$ 27 / (($\sqrt{3}$)⁵ $\times$ ($\sqrt{3}$)⁴).
- Note 27 = ($\sqrt{3}$)⁶. Numerator ($\sqrt{3}$)⁴ $\times$ ($\sqrt{3}$)⁶ = ($\sqrt{3}$)¹⁰ ; denominator ($\sqrt{3}$)⁹ ; result ($\sqrt{3}$)¹ = $\sqrt{3}$.
Example 3 : If 3ˣ = 5, find 3ˣ⁺¹.
- 3ˣ⁺¹ = 3ˣ $\times$ 3¹ = 5 $\times$ 3 = 15.
Example 4 : Simplify (36)ⁿ $\times$ (5)²ⁿ / (30)²ⁿ.
- 36 = 6² $\rightarrow$ 6²ⁿ ; 5²ⁿ ; 30 = 6 $\times$ 5 $\rightarrow$ 30²ⁿ = 6²ⁿ $\times$ 5²ⁿ $\rightarrow$ result = 1.
Lesson Summary
Key Concepts with Solved Examples
1Zero and Negative Exponents
1 Example 1
Evaluate 5^0 + 2^(-2).
- 15^0 = 1 (any non-zero number to power 0 = 1)
- 22^(-2) = 1/2^2 = 1/4
- 21 + 1/4 = 5/4
Final Answer: 5/4
2 Example 2
Simplify (3^(-2))(9^2).
- 23^(-2) = 1/9
- 29^2 = 81
- 2(1/9)(81) = 9
Final Answer: 9
2Product, Quotient, and Power Rules
1 Example 1
Simplify x^3 * x^5 / x^2.
- 2Product rule: x^3 * x^5 = x^(3+5) = x^8
- 2Quotient rule: x^8 / x^2 = x^(8-2) = x^6
Final Answer: x^6
2 Example 2
Simplify (2a^3)^2 * (a^2)^3.
- 2(2a^3)^2 = 4a^6
- 2(a^2)^3 = a^6
- 24a^6 * a^6 = 4a^12
Final Answer: 4a^12
3Evaluating Exponential Expressions
1 Example 1
If 2^x = 8, find 2^(x+1).
- 22^x = 8 = 2^3 $\rightarrow$ x = 3
- 22^(x+1) = 2^(3+1) = 2^4 = 16
Final Answer: 16
2 Example 2
If 3^x = 5, find 3^(2x).
- 23^(2x) = (3^x)^2 = 5^2 = 25
Final Answer: 25