Simplifying Logarithms: Troubleshooting Common Mistakes

  • Thread starter Rectifier
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In summary, when simplifying the equation y=ln(2x), it should result in e^y=2x, not e^y=2+x as shown in the first equation. The mistake is in the third step where instead of adding the exponents, they should have been multiplied.
  • #1
Rectifier
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Hey there!
I am getting two completely different equations when I try to simplify one.
What am I doing wrong?

1.
[tex]y=ln(2x) \ \Leftrightarrow \ y=ln(2) + ln(x) \ \Leftrightarrow \ e^y=e^{ln(2)}+e^{ln(x)} \ \Leftrightarrow \ e^y=2+x [/tex]

2.
[tex]y=ln(2x) \ \Leftrightarrow \ e^y=e^{ln(2x)} \ \Leftrightarrow \ e^y=2x [/tex]

I am sorry if its something completely obvious. Its pretty late here so my brain doesn't function properly :)
 
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  • #2
Rectifier said:
Hey there!
I am getting two completely different equations when I try to simplify one.
What am I doing wrong?

1.
[tex]y=ln(2x) \ \Leftrightarrow \ y=ln(2) + ln(x) \ \Leftrightarrow \ e^y=e^{ln(2)}+e^{ln(x)} \ \Leftrightarrow \ e^y=2+x [/tex]
It should be ##e^{ln(2) + ln(x)} = e^{ln(2)} \cdot e^{ln(x)} ## in your third step.
Rectifier said:
2.
[tex]y=ln(2x) \ \Leftrightarrow \ e^y=e^{ln(2x)} \ \Leftrightarrow \ e^y=2x [/tex]

I am sorry if its something completely obvious. Its pretty late here so my brain doesn't function properly :)
 
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  • #3
Oh! Thank you Mark!
 

FAQ: Simplifying Logarithms: Troubleshooting Common Mistakes

What is a logarithm?

A logarithm is a mathematical function that represents the number of times a certain value needs to be multiplied by itself to reach a given number. It is the inverse function of exponentiation, which means that it undoes the effect of an exponent.

What are the common mistakes when simplifying logarithms?

Some common mistakes when simplifying logarithms include forgetting to apply the exponent rule, mixing up the base and the argument, and not using the properties of logarithms correctly. It is also important to remember to simplify the expression using basic algebra techniques before applying logarithm rules.

How do I know if I have simplified a logarithm correctly?

To check if a logarithm has been simplified correctly, you can use a calculator to evaluate the original expression and the simplified expression. They should give the same result. You can also use the properties of logarithms to expand the simplified expression and see if it matches the original expression.

Can I simplify a logarithm with a negative argument?

No, you cannot simplify a logarithm with a negative argument. Logarithms are only defined for positive numbers, so if the argument is negative, the logarithm is undefined. However, if the argument is a fraction or a decimal, you can simplify it using the properties of logarithms.

Are there any tips for simplifying logarithms?

One tip for simplifying logarithms is to always check the answer after simplifying. Another helpful tip is to use the properties of logarithms to break the expression into smaller parts and then simplify each part individually. It is also important to practice and become familiar with the properties and rules of logarithms to avoid common mistakes.

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