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Question

For integers $a$, $b$ and $c$, what would be the minimum and maximum values respectively of $a + b + c$ if $\log |a| + \log |b| + \log |c| = 0$?

The correct answer is
-3 and 3

Solving for Minimum and Maximum Integer Sum

The problem asks for the minimum and maximum values of the sum $a + b + c$, where $a$, $b$, and $c$ are integers satisfying the equation $\log |a| + \log |b| + \log |c| = 0$.

Understanding the Logarithm Condition

Using the properties of logarithms, we can simplify the given equation:

  • The sum of logarithms is the logarithm of the product: $\log (|a| \cdot |b| \cdot |c|) = 0$
  • Exponentiating both sides with base 10 (or simply using the definition of logarithm): $|a| \cdot |b| \cdot |c| = 10^0$
  • Therefore, the condition simplifies to: $|a| \cdot |b| \cdot |c| = 1$

Determining Integer Constraints

Since $a$, $b$, and $c$ are integers, their absolute values $|a|$, $|b|$, and $|c|$ must be positive integers. The only way the product of three positive integers can equal 1 is if each integer is equal to 1.

  • $|a| = 1 \implies a = 1$ or $a = -1$
  • $|b| = 1 \implies b = 1$ or $b = -1$
  • $|c| = 1 \implies c = 1$ or $c = -1$

Calculating Minimum and Maximum Sums

To find the minimum value of $a + b + c$, we choose the smallest possible integer values for $a$, $b$, and $c$.

  • Minimum sum: Set $a = -1$, $b = -1$, $c = -1$. $a + b + c = (-1) + (-1) + (-1) = -3$

To find the maximum value of $a + b + c$, we choose the largest possible integer values for $a$, $b$, and $c$.

  • Maximum sum: Set $a = 1$, $b = 1$, $c = 1$. $a + b + c = 1 + 1 + 1 = 3$

The minimum value is -3 and the maximum value is 3.

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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. The value of the expression $\frac{1}{1+\log_u vw} + \frac{1}{1+\log_v wu} + \frac{1}{1+\log_w uv}$ is
  5. If $\log_x (5/7) = -1/3$, then the value of $x$ is
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