26,208 views
2 votes
2 votes
Use the change of base formula to compute log314.Round your answer to the nearest thousandth.

Use the change of base formula to compute log314.Round your answer to the nearest-example-1
User Marc Audet
by
2.9k points

1 Answer

9 votes
9 votes

Hello there. To solve this question, we'll have to remember some properties about changing bases in logarithms.

Given the logarithm:


\log_3\left((1)/(4)\right)

We first use the properties:


\begin{gathered} \log_c\left((a)/(b)\right)=\log_c(a)-\log_c(b)\text{ and } \\ \\ \log_c(1)=0,0In this case, we get:<p></p>[tex]\begin{gathered} \log_3\left((1)/(4)\right)=\log_3(1)-\log_3(4)=0-\log_3(4) \\ \\ \Rightarrow-\log_3(4) \end{gathered}

Now, we use the change of basis formula:


\log_c(a)=(\log_d(a))/(\log_d(c))

When changing for a basis d greater than zero and not equal to 1.

With this, we have that


-\log_3(4)=-(\log_(10)(4))/(\log_(10)(3))

Applying the property:


\log_c(a^b)=b\cdot\log_c(a)

and knowing that 4 = 2², we get


-(2\log_(10)(2))/(\log_(10)(3))

We chose base 10 log because we know the following values for:


\begin{gathered} \log_(10)(2)\approx0.3010 \\ \\ \log_(10)(3)\approx0.477 \end{gathered}

Hence the approximation for what we want is


\log_3\left((1)/(4)\right)\approx-(2\cdot0.3010)/(0.477)=-1.262

This is the answer we're looking for.

User Ajit Panigrahi
by
2.9k points