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Question

Real numbers $y$, $p$, and $n$ (all greater than 1) satisfy
$$(\log_{p^{1/n}} y)(\log_{y^{1/n}} p) = 16,$$
where the logarithms are taken to the bases $p^{1/n}$ and $y^{1/n}$.
The value of $n$ is ________

The correct answer is
4

Solving the Logarithm Equation

We are given the equation involving real numbers $y, p, n$ (all greater than 1):

$(\log_{p^{1/n}} y)(\log_{y^{1/n}} p) = 16$

We need to find the value of $n$. Let's simplify the logarithmic terms using logarithm properties.

Logarithm Property Application

Recall the logarithm property: $\log_{a^k} b = \frac{1}{k} \log_a b$. Applying this to our terms:

  • The first term: $\log_{p^{1/n}} y = \frac{1}{1/n} \log_p y = n \log_p y$
  • The second term: $\log_{y^{1/n}} p = \frac{1}{1/n} \log_y p = n \log_y p$

Substitute these simplified terms back into the original equation:

$(n \log_p y)(n \log_y p) = 16$ $n^2 (\log_p y)(\log_y p) = 16$

Simplifying to Find n

Now, use the change of base property for logarithms: $\log_a b = \frac{1}{\log_b a}$. This means $\log_y p = \frac{1}{\log_p y}$. Substitute this into the equation:

$n^2 (\log_p y) \left(\frac{1}{\log_p y}\right) = 16$

The term $(\log_p y)$ cancels out (since $y > 1$, $\log_p y$ is non-zero):

$n^2 = 16$

To find $n$, we take the square root of both sides:

$n = \pm \sqrt{16}$ $n = \pm 4$

The problem states that $n > 1$. Therefore, we choose the positive value.

$n = 4$

Final Answer Determination

The value of $n$ that satisfies the given conditions is 4.

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Important Questions from Logarithms

  1. For positive non-zero real variables $p$ and $q$, if 
    $\log (p^2 + q^2) = \log p + \log q + 2 \log 3$, 
    then, the value of $\frac{p^4+q^4}{p^2q^2}$ is

  2. For a real number $x > 1$, 
    $\frac{1}{\log_2 x} + \frac{1}{\log_3 x} + \frac{1}{\log_4 x} = 1$ 
    The value of $x$ is

  3. A petrified wood fossil was discovered with 8 g of $^{14}C$. The decay of $^{14}C$ over time is given by: 

    $N_T = N_0 e^{-0.0001216T}$ 

    If the half-life of $^{14}C$ is 5700 years, and the fossil initially had 32 g of $^{14}C$, the age of the fossil in years is ______.

  4. For integers $a$, $b$ and $c$, what would be the minimum and maximum values respectively of $a + b + c$ if $\log |a| + \log |b| + \log |c| = 0$?
  5. The value of the expression $\frac{1}{1+\log_u vw} + \frac{1}{1+\log_v wu} + \frac{1}{1+\log_w uv}$ is
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