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Let f open parentheses x close parentheses equals ln open parentheses x squared close parentheses space space space a n d space space space g open parentheses x close parentheses equals square root of e to the power of 3 x end exponent end root. Find f o g open parentheses x close parentheses and its domain?

User Worksology
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1 Answer

6 votes

Answer:


(f\ o\ g)(x) = 3x


-\infty < x < \infty

Explanation:

See comment for right presentation of question

Given


f(x) = ln(x^2)


g(x)=\sqrt{e^(3x)}

Solving (a): (f o g)(x)

This is calculated as:


(f\ o\ g)(x) = f(g(x))

We have:


f(x) = ln(x^2)


f(g(x)) = \ln((g(x))^2)

Substitute:
g(x)=\sqrt{e^(3x)}


f(g(x)) = \ln(\sqrt{e^(3x)})^2

Evaluate the square


f(g(x)) = \ln(e^(3x))

Using laws of natural logarithm:


\ln(e^(ax)) = ax

So:


f(g(x)) = \ln(e^(3x))


f(g(x)) = 3x

Hence:


(f\ o\ g)(x) = 3x

Solving (b): The domain

We have:


f(g(x)) = 3x

The above function has does not have any undefined points and domain constraints.

Hence, the domain is:
-\infty < x < \infty

User James Coote
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