Solve the Logarithm Product: log₃7 × log₇9 Step-by-Step

Question

log37×log79= \log_37\times\log_79=

Video Solution

Solution Steps

00:00 Solve
00:04 We will use the formula for multiplication of logarithms
00:12 We will switch between the bases of the logarithms
00:22 We will use this formula in our exercise
00:28 Let's calculate the first logarithm
00:49 This is the solution for the first logarithm, let's substitute in the exercise and solve
01:11 And this is the solution to the question

Step-by-Step Solution

To solve the expression log37×log79 \log_3 7 \times \log_7 9 , we use a known logarithmic property. This property states that:

logab×logbc=logac \log_a b \times \log_b c = \log_a c

Applying this property allows us to simplify:

log37×log79=log39 \log_3 7 \times \log_7 9 = \log_3 9

Next, we need to calculate log39 \log_3 9 . Since 9 can be expressed as 32 3^2 , we have:

log39=log3(32) \log_3 9 = \log_3(3^2)

Using the power rule of logarithms, logb(xn)=nlogbx \log_b (x^n) = n \cdot \log_b x , we find:

log3(32)=2log33 \log_3(3^2) = 2 \cdot \log_3 3

Since log33=1 \log_3 3 = 1 , it follows that:

21=2 2 \cdot 1 = 2

Therefore, the value of log37×log79 \log_3 7 \times \log_7 9 is 2 2 .

The correct answer choice is therefore Choice 3: 2 2 .

Answer

2 2


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