Math Problem Statement

Use the Laws of Logarithms to evaluate the expression. log3(15) − log3(35) + log3(189)

Solution

We are tasked with simplifying and evaluating the expression:

log3(15)log3(35)+log3(189)\log_3(15) - \log_3(35) + \log_3(189)

Step 1: Apply the Laws of Logarithms

We can use the following logarithmic properties:

  1. Difference of logs:
    logb(x)logb(y)=logb(xy)\log_b(x) - \log_b(y) = \log_b\left(\frac{x}{y}\right)

  2. Sum of logs:
    logb(x)+logb(y)=logb(xy)\log_b(x) + \log_b(y) = \log_b(xy)

Now, let's first combine the terms log3(15)log3(35)\log_3(15) - \log_3(35):

log3(15)log3(35)=log3(1535)\log_3(15) - \log_3(35) = \log_3\left(\frac{15}{35}\right)

We can simplify the fraction 1535\frac{15}{35}:

1535=37\frac{15}{35} = \frac{3}{7}

So the expression becomes:

log3(37)+log3(189)\log_3\left(\frac{3}{7}\right) + \log_3(189)

Step 2: Apply the Sum of Logs Rule

Now, use the sum rule to combine the two logarithms:

log3(37)+log3(189)=log3(37×189)\log_3\left(\frac{3}{7}\right) + \log_3(189) = \log_3\left(\frac{3}{7} \times 189\right)

Step 3: Simplify the Product

Next, calculate the product:

37×189=3×1897=5677=81\frac{3}{7} \times 189 = \frac{3 \times 189}{7} = \frac{567}{7} = 81

Thus, the expression simplifies to:

log3(81)\log_3(81)

Step 4: Evaluate the Logarithm

Finally, since 81=3481 = 3^4, we have:

log3(81)=log3(34)=4\log_3(81) = \log_3(3^4) = 4

Final Answer:

log3(15)log3(35)+log3(189)=4\log_3(15) - \log_3(35) + \log_3(189) = 4


Would you like further clarification or any details? Here are some related questions you may find interesting:

  1. How do the properties of logarithms help to simplify expressions like this?
  2. What happens if the base of the logarithms changes, for example to base 10 or base ee?
  3. How can we apply the laws of logarithms to solve equations involving logarithms?
  4. What is the inverse of a logarithmic function, and how does it relate to exponential functions?
  5. Can we apply the logarithmic laws to expressions with different bases (e.g., log2(8)\log_2(8))?

Tip: When simplifying logarithmic expressions, always look for opportunities to use the product, quotient, and power rules.

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Math Problem Analysis

Mathematical Concepts

Logarithms
Properties of Logarithms
Simplification of Expressions

Formulas

log_b(x) - log_b(y) = log_b(x/y)
log_b(x) + log_b(y) = log_b(x * y)
log_b(x^k) = k * log_b(x)

Theorems

Properties of Logarithms

Suitable Grade Level

Grades 9-12