AQA A Level Maths: Pure复习笔记6.2.1 Laws of Logarithms

Laws of Logarithms

What are the laws of logarithms?

6.2.1-Laws-of-Logarithms-Notes-fig1

6.2.1-Laws-of-Logarithms-Notes-fig2

6.2.1-Laws-of-Logarithms-Notes-fig3

  • Two of these were seen in the notes Logarithmic Functions
  • Beware …
    • … log (x + y) ≠ log x + log y
  • Results apply to ln too

How do I use the laws of logarithms?

  • Laws of logarithms can be used to …
    • … simplify expressions
    • … solve logarithmic equations
    • … solve exponential equations

    6.2.1-Laws-of-Logarithms-Notes-fig4

Exam Tip

  • Remember to check whether your solutions are valid
    • log (x+k) is only defined if x > -k
    • You will lose marks if you forget to reject invalid solutions

Worked Example

6.2.1-Laws-of-Logarithms-Example-fig1

 

 

 

 

 

 

 

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