Problem 98 - College Algebra

Question

Evaluate or simplify each expression without using a calculator. $$ e^{\ln 7 x^{2}} $$

Step-by-Step Solution

Answer

The simplified form of the given expression would be \(7x^{2}\)

Step 1 - Apply Exp and Logarithm property

Apply the property of exponential and logarithm \(e^{ln x} = x\). Here, \(x\) is \(7x^{2}\). So, replace the given expression \(e^{ln 7x^{2}}\) with \(7x^{2}\)

Step 2: Identify the relevant trigonometric identities

Based on the given expression or equation, identify which trigonometric identities (Pythagorean, double-angle, sum/difference, etc.) are applicable.

Step 3: Apply the identities and simplify

Apply the identified identities to transform the expression. Simplify step by step, combining like terms and reducing fractions where possible.

Step 4: Solve or evaluate

If solving an equation, isolate the trigonometric function and find the angle(s). If evaluating, compute the final numerical value.

Step 5: State the result

Express the final answer, including all solutions in the required domain if solving an equation.

Step 6: Conclude with the answer

The simplified form of the given expression would be \(7x^{2}\)

Key Concepts

Natural Logarithm

The natural logarithm is a logarithm to the base of the number \( e \), which is an irrational constant approximately equal to 2.71828. The notation for natural logarithm is \( \ln \). When you see \( \ln(x) \), it means you are looking for a power to which \( e \) must be raised to get \( x \).
Why is this useful? Because in many natural growth and decay processes, such as population growth and radioactive decay, the natural logarithm comes into play. The natural logarithm can simplify complex exponentiation problems.
For example, if you have \( e^{\ln(7x^2)} \), you can use the property that \( e^{\ln(y)} = y \). This means our expression simplifies directly to \( 7x^2 \). In essence, \( e \) and \( \ln \) are inverse functions, cancelling each other out in the exponentiation context.

Exponentiation

Exponentiation is a mathematical operation involving two numbers, the base and the exponent. It can be written in the form \( a^b \), where \( a \) is the base and \( b \) is the exponent. This denotes that the base \( a \) is multiplied by itself \( b \) times.
Exponentiation has key properties, such as:

• The product of powers: \( a^m \times a^n = a^{m+n} \)
• The power of a power: \( (a^m)^n = a^{m \cdot n} \)
• Zero exponent rule: For any non-zero \( a \), \( a^0 = 1 \)

When exponentiation is combined with logarithms, it often simplifies calculations. In the expression \( e^{\ln(7x^2)} \), the properties of exponentiation allow the simplification using the relationship \( e^{\ln(y)} = y \), thus resulting directly in \( 7x^2 \). This powerful property helps in quickly evaluating expressions that otherwise could become quite complex.

Properties of Logarithms

Logarithms are closely related to exponentiation and have several fundamental properties that make calculations simpler:

• Product Property: \( \log_b(xy) = \log_b(x) + \log_b(y) \)
• Quotient Property: \( \log_b\left(\frac{x}{y}\right) = \log_b(x) - \log_b(y) \)
• Power Property: \( \log_b(x^y) = y \cdot \log_b(x) \)
• Change of Base Formula: \( \log_b(x) = \frac{\log_c(x)}{\log_c(b)} \)

Understanding these properties lets you break down complex logarithmic expressions into simpler components. In practice, with an expression such as \( e^{\ln(7x^2)} \), you leverage the inverse relationship between exponentials and natural logarithms to simplify or even compute the values directly. The interplay of the exponential function \( e \) and the natural log \( \ln \) showcases these logarithmic properties beautifully, simplifying what initially seems like a complex calculation to an easily graspable result.