Math Problem Statement

Use properties of logarithms to evaluate the expression without using a calculator: 5log_{25}(5) - 4log_{25}(5) + log_{25}(1/625) = ?

Solution

Let's break down the expression using properties of logarithms and solve it step by step:

The given expression is:

5log25(5)4log25(5)+log25(1625)5\log_{25}(5) - 4\log_{25}(5) + \log_{25}\left(\frac{1}{625}\right)

Step 1: Combine like terms

The first two terms both involve log25(5)\log_{25}(5). So, we can simplify them as follows:

(54)log25(5)=log25(5)(5 - 4)\log_{25}(5) = \log_{25}(5)

Step 2: Evaluate log25(5)\log_{25}(5)

Recall that 25=5225 = 5^2, so:

log25(5)=12\log_{25}(5) = \frac{1}{2}

Thus, the expression becomes:

12+log25(1625)\frac{1}{2} + \log_{25}\left(\frac{1}{625}\right)

Step 3: Simplify log25(1625)\log_{25}\left(\frac{1}{625}\right)

First, express 625625 as a power of 2525. Since 625=252625 = 25^2, we can rewrite the logarithm as:

log25(1625)=log25(252)\log_{25}\left(\frac{1}{625}\right) = \log_{25}(25^{-2})

By the logarithmic power rule, logb(xn)=nlogb(x)\log_b(x^n) = n \log_b(x), this becomes:

log25(252)=2log25(25)\log_{25}(25^{-2}) = -2 \log_{25}(25)

Since log25(25)=1\log_{25}(25) = 1, the expression simplifies to:

2-2

Step 4: Combine everything

Now, substitute back into the expression:

122=1242=32\frac{1}{2} - 2 = \frac{1}{2} - \frac{4}{2} = -\frac{3}{2}

Thus, the value of the expression is:

32\boxed{-\frac{3}{2}}

Would you like further details on any of the steps?

Here are 5 related questions for further exploration:

  1. How do the logarithmic properties apply when changing bases?
  2. Can you explain why log25(25)\log_{25}(25) equals 1?
  3. What is the logarithmic rule for division and powers?
  4. How would you solve if the base was different, like log5\log_5?
  5. How does this simplify when logarithmic arguments are fractions?

Tip: Always try breaking down the expression using basic logarithmic identities like the product, quotient, and power rules before simplifying further.

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Math Problem Analysis

Mathematical Concepts

Logarithms
Properties of Logarithms
Exponentiation

Formulas

log_b(x^n) = n * log_b(x)
log_b(b) = 1

Theorems

Logarithmic Power Rule
Logarithmic Identity: log_b(b) = 1

Suitable Grade Level

Grades 9-12