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Use properties of logarithms to condense logarithmic expression. Write the expression as a single logarithm whose coefficient is 1. Where possible, evaluate logarithmic expressions without using a calculator. \(\log x+\log \left(x^{2}-4\right)-\log 15-\log (x+2)\)

Short Answer

Expert verified
The simplified expression is \(log[(x(x-2)) / 15]\)

Step by step solution

01

Apply the logarithmic properties

First, use the property of logarithms \(log(a) + log(b) = log(ab)\) and \(log(a) - log(b) = log(a/b)\). From this, the given expression \(log(x) + log(x^2 - 4) - log(15) - log(x + 2)\) can be rearranged as \(log(x(x^2 - 4)) - log(15(x + 2))\). It simplifies to \(log[(x(x^2 - 4)) / (15(x + 2))]\)
02

Further Simplifying the Expression

We notice in the nominator that \((x^2-4)\) can be factored into \((x+2)(x-2)\) using the difference of squares rule. Our expression inside the logarithm becomes \(log([(x(x+2)(x-2)) / (15(x + 2))])\). Because (x + 2) appears in both nominator and denominator, it gets cancelled out. Finally, the expression within the logarithm simplifies to \(log[(x(x-2)) / 15]\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Properties of Logarithms
Understanding the properties of logarithms is crucial when you need to manipulate and simplify logarithmic expressions. Logarithms have unique properties that allow us to condense multiple logarithmic terms into a single term. For instance, the property \(\log(a) + \log(b) = \log(ab)\) lets us combine two logs with an addition sign into one by multiplying their arguments. Similarly, the property \(\log(a) - \log(b) = \log(\frac{a}{b})\) allows for the combination of two logarithmic terms with a subtraction sign into one by dividing their arguments. These properties can make complex-looking logarithmic expressions much cleaner and easier to work with. They also set the stage for further simplification steps, especially when combined with other algebraic methods such as factoring or expanding.

For algebraic manipulation, there are more properties like the power rule \(\log(a^n) = n\log(a)\) that can help in simplifying complexities within the logarithms further. It's important to apply these properties carefully to avoid errors and to recognize which property fits the expression best for a successful simplification process.
Logarithmic Expression Simplification
When it comes to logarithmic expression simplification, the goal is to express complex logarithmic statements in a more straightforward, condensed form. This often involves the use of the aforementioned properties of logarithms. Simplifying a logarithmic expression not only makes it easier to analyze and understand but sometimes also helps to solve for variables or evaluate the expression without the need for a calculator. After applying the properties correctly to combine logarithms, you might find that the resulting terms can be further simplified by identifying common factors in the numerator and the denominator or by recognizing opportunities to factorize algebraic expressions.

It is also important to note that simplifying logarithmic expressions sometimes includes dealing with expressions where the arguments of the logarithms are algebraic expressions themselves. In such cases, applying algebraic skills like factoring polynomials or canceling out like terms is necessary. The simplification of the logarithmic expressions greatly depends on recognizing and efficiently applying these algebraic operations in tandem with the logarithmic properties.
Difference of Squares
The difference of squares is a pivotal concept in algebra that comes into play when factoring polynomials. It refers to the fact that a difference between two square terms, such as \( a^2 - b^2 \), can be factored into the product of the sum and difference of the two terms: \( (a + b)(a - b) \). This formula is valuable in simplifying and reducing expressions, as seen in the original textbook exercise. Factoring with the difference of squares can often reveal opportunities to cancel out terms when the expression is part of a larger fraction or used within a logarithm.

If students carefully employ the difference of squares rule in appropriate contexts, it becomes a powerful tool to make expressions more manageable, leading to straightforward paths for further evaluation and simplification. This rule is not only limited to its direct application but can also be useful in recognizing patterns in higher-order polynomials that could be rewritten in forms amenable to the difference of squares factorization.

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Most popular questions from this chapter

The bar graph indicates that the percentage of fi rst-year college students expressing antifeminist views declined after 1970. CAN'T COPY THE GRAPH The function $$f(x)=-4.82 \ln x+32.5$$ models the percentage of first-year college women, \(f(x)\) expressing antifeminist views (by agreeing with the statement) \(x\) years after 1969 a. Use the function to find the percentage of first-year college women expressing antifeminist views in 2008 . Round to one decimal place. Does this function value overestimate or underestimate the percentage displayed by the graph? By how much? b. Use the function to project the percentage of first-year college women who will express antifeminist views in \(2015 .\) Round to one decimal place.

Check each proposed solution by direct substitution or with a graphing utility. $$\ln (\ln x)=0$$

Hurricanes are one of nature's most destructive forces. These low-pressure areas often have diameters of over 500 miles. The function \(f(x)=0.48 \ln (x+1)+27\) models the barometric air pressure, \(f(x),\) in inches of mercury, at a distance of \(x\) miles from the eye of a hurricane. The function \(P(t)=145 e^{-0.092 t}\) models a runner's pulse, \(P(t),\) in beats per minute, \(t\) minutes after a race, where \(0 \leq t \leq 15 .\) Graph the function using a graphing utility. TRACE along the graph and determine after how many minutes the runner's pulse will be 70 beats per minute. Round to the nearest tenth of a minute. Verify your observation algebraically.

Describe the following property using words: \(\log _{b} b^{x}=x\).

Evaluate the indicated logarithmic expressions without using a calculator. a. Evaluate: \(\log _{3} 81\) b. Evaluate: \(2 \log _{3} 9\) c. What can you conclude about $$\log _{3} 81, \text { or } \log _{3} 9^{2} ?$$

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