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Question

The value of the expression $\frac{1}{1+\log_u vw} + \frac{1}{1+\log_v wu} + \frac{1}{1+\log_w uv}$ is

The correct answer is
1

Simplifying the Logarithmic Expression

The problem asks for the value of the expression:

$ E = \frac{1}{1+\log_u vw} + \frac{1}{1+\log_v wu} + \frac{1}{1+\log_w uv} $

We can simplify each term using logarithm properties. Recall that $1 = \log_b b$ for any base $b$. Let's rewrite the denominators:

  • Term 1 Denominator: $1+\log_u vw = \log_u u + \log_u vw = \log_u (u \cdot vw) = \log_u (uvw)$
  • Term 2 Denominator: $1+\log_v wu = \log_v v + \log_v wu = \log_v (v \cdot wu) = \log_v (uvw)$
  • Term 3 Denominator: $1+\log_w uv = \log_w w + \log_w uv = \log_w (w \cdot uv) = \log_w (uvw)$

Now, substitute these back into the expression:

$ E = \frac{1}{\log_u (uvw)} + \frac{1}{\log_v (uvw)} + \frac{1}{\log_w (uvw)} $

Applying Change of Base Property

Using the logarithm property $\frac{1}{\log_a b} = \log_b a$, we can rewrite the expression:

$ E = \log_{uvw} u + \log_{uvw} v + \log_{uvw} w $

Combining Logarithms and Final Value

Using the logarithm property $\log_b x + \log_b y + \log_b z = \log_b (xyz)$, we combine the terms:

$ E = \log_{uvw} (u \cdot v \cdot w) $

$ E = \log_{uvw} (uvw) $

Finally, using the property $\log_b b = 1$:

$ E = 1 $

Therefore, the value of the expression is 1.

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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. If $\log_x (5/7) = -1/3$, then the value of $x$ is
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