Math Problem Statement

given that log3 = x and log5 = y, express log4.5 in terms of x and y

Solution

We are given:

log3=xandlog5=y\log 3 = x \quad \text{and} \quad \log 5 = y

We need to express log4.5\log 4.5 in terms of xx and yy.

Start by expressing 4.54.5 as a product:

4.5=924.5 = \frac{9}{2}

Thus,

log4.5=log(92)\log 4.5 = \log \left( \frac{9}{2} \right)

Using the logarithmic property:

log(ab)=logalogb\log \left( \frac{a}{b} \right) = \log a - \log b

We can write:

log4.5=log9log2\log 4.5 = \log 9 - \log 2

Now, log9\log 9 can be written as log9=log(32)\log 9 = \log (3^2), and using the logarithmic power rule log(ab)=bloga\log (a^b) = b \log a, we get:

log9=2log3\log 9 = 2 \log 3

Substitute log3=x\log 3 = x:

log9=2x\log 9 = 2x

So,

log4.5=2xlog2\log 4.5 = 2x - \log 2

Next, we need to express log2\log 2 in terms of xx and yy. Since log10=1\log 10 = 1, we use the approximation:

log10=log2+log5\log 10 = \log 2 + \log 5

Thus:

1=log2+y1 = \log 2 + y

Solving for log2\log 2:

log2=1y\log 2 = 1 - y

Finally, substitute this into the expression for log4.5\log 4.5:

log4.5=2x(1y)\log 4.5 = 2x - (1 - y)

Simplify:

log4.5=2x1+y\log 4.5 = 2x - 1 + y

Thus, the expression for log4.5\log 4.5 in terms of xx and yy is:

log4.5=2x+y1\log 4.5 = 2x + y - 1


Would you like further explanation on any of these steps or details on logarithmic properties?

Here are 5 related questions:

  1. How can you express log(ab)\log (a \cdot b) using logarithmic rules?
  2. What is the logarithmic power rule, and how does it apply to log(32)\log(3^2)?
  3. How would you express log(7.5)\log (7.5) in terms of xx and yy?
  4. What is the relationship between common logarithms (base 10) and natural logarithms (base ee)?
  5. How does the change of base formula work in logarithms?

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

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Math Problem Analysis

Mathematical Concepts

Logarithms
Logarithmic Properties

Formulas

log(a/b) = log(a) - log(b)
log(a^b) = b * log(a)
log(10) = log(2) + log(5)

Theorems

Logarithmic Quotient Rule
Logarithmic Power Rule

Suitable Grade Level

Grades 10-12