Math Problem Statement

Jika log base 7 dari 2 sama dengan a dan log base 2 dari 3 sama dengan b, maka log base 6 dari 98 adalah ....

Solution

We are given the following information in the image:

log72=aandlog23=b\log_7 2 = a \quad \text{and} \quad \log_2 3 = b We need to find log698\log_6 98 in terms of aa and bb.

Solution:

  1. Expressing log698\log_6 98 using logarithmic properties: log698=log98log6\log_6 98 = \frac{\log 98}{\log 6}

  2. Breaking down log98\log 98: 98=2×49=2×7298 = 2 \times 49 = 2 \times 7^2 Therefore, log98=log(2×72)=log2+2log7\log 98 = \log (2 \times 7^2) = \log 2 + 2 \log 7

  3. Breaking down log6\log 6: 6=2×36 = 2 \times 3 Therefore, log6=log(2×3)=log2+log3\log 6 = \log (2 \times 3) = \log 2 + \log 3

  4. Substituting known values for log72=a\log_7 2 = a and log23=b\log_2 3 = b:

    From the given information:

    \quad \text{and} \quad \log_2 3 = b \implies \log 3 = b \log 2$$ Using these in the equations for $$\log 98$$ and $$\log 6$$: $$\log 98 = \log 2 + 2 \cdot \frac{\log 2}{a}$$ $$\log 6 = \log 2 + b \log 2 = \log 2 (1 + b)$$
  5. Final expression for log698\log_6 98: log698=log2+2log2alog2(1+b)\log_6 98 = \frac{\log 2 + 2 \cdot \frac{\log 2}{a}}{\log 2 (1 + b)}

    Factor out log2\log 2 in both the numerator and the denominator: log698=log2(1+2a)log2(1+b)=1+2a1+b\log_6 98 = \frac{\log 2 \left( 1 + \frac{2}{a} \right)}{\log 2 (1 + b)} = \frac{1 + \frac{2}{a}}{1 + b}

Thus, the answer is: a+2a(b+1)\boxed{ \frac{a + 2}{a(b + 1)} }

So the correct answer is option C.


Would you like more details or have any further questions? Here are 5 related questions to deepen your understanding:

  1. What are the logarithmic properties used to simplify log(2×72)\log(2 \times 7^2)?
  2. How does the change of base formula work for logarithms?
  3. How can you derive logarithms in terms of different bases from a given logarithmic relationship?
  4. What would log5100\log_5 100 be if you are given log52\log_5 2 and log55\log_5 5?
  5. How can logarithms help simplify exponential equations?

Tip: Always simplify logarithmic expressions by breaking them down into known components using logarithmic identities.

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Math Problem Analysis

Mathematical Concepts

Logarithms
Logarithmic Properties
Change of Base Formula

Formulas

log_b(xy) = log_b(x) + log_b(y)
log_b(x^n) = n log_b(x)
Change of Base Formula: log_b(a) = log_c(a) / log_c(b)

Theorems

Properties of Logarithms
Change of Base Theorem

Suitable Grade Level

Grades 10-12