Common Core: High School - Functions : Express Exponential Models as Logarithmic Solutions: CCSS.Math.Content.HSF-LE.A.4

Study concepts, example questions & explanations for Common Core: High School - Functions

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All Common Core: High School - Functions Resources

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Example Questions

Example Question #341 : High School: Functions

Solve for \(\displaystyle x\) using rules of logarithmic functions.

\(\displaystyle e^{x-4}-1=0\)

Possible Answers:

\(\displaystyle x=2\)

\(\displaystyle x=\ln2\)

\(\displaystyle x=3\)

\(\displaystyle x=\ln1\)

\(\displaystyle x=4\)

Correct answer:

\(\displaystyle x=4\)

Explanation:

This question is testing one's ability to understand logarithmic rules and apply them in order to solve a function.

For the purpose of Common Core Standards, "For exponential models, express as a logarithm the solution to ab^(ct) = d where ac, and dare numbers and the base b is 2, 10, or e; evaluate the logarithm using technology." falls within the Cluster A of "Construct and compare linear, quadratic, and exponential models and solve problems" concept (CCSS.MATH.CONTENT.HSF-LE.A.4). 

Knowing the standard and the concept for which it relates to, we can now do the step-by-step process to solve the problem in question.

Step 1: Use algebraic operations to manipulate the function and isolate the \(\displaystyle x\) value on one side of the equation.

\(\displaystyle e^{x-4}-1=0\)

Add one from both sides.

\(\displaystyle \\e^{x-4}-1+1=0+1 \\e^{x-4}=1\)

Step 2: Identify logarithmic rules.

Recall that \(\displaystyle \ln e=1\) and \(\displaystyle \ln1=0\)

Step 3: Apply logarithmic rules to solve for \(\displaystyle x\)

\(\displaystyle \\e^{x-4}=1 \\ \ln e^{x-4}=\ln 1\\ x-4=\ln 1\\x=\ln 1+4\\x=0+4\\x=4\)

All Common Core: High School - Functions Resources

6 Diagnostic Tests 82 Practice Tests Question of the Day Flashcards Learn by Concept
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