Problem 31 - Contemporary Precalculus

Question

Evaluate the given expression without using a calculator. $$e^{\ln 931}$$

Step-by-Step Solution

Answer

Answer: The value of the expression $$e^{\ln 931}$$ is 931.

Step 1: Recall the property of e and natural logarithms

The expression we are given involves the base e and the natural logarithm, ln. The main property to remember is that for any positive number x: $$e^{\ln{x}} = x$$ This property can be thought of as the inverse relationship between exponentiation and logarithms.

Step 2: Apply the property to the given expression

Now let's apply this property directly to the given expression: $$e^{\ln 931}$$ Here, we have x = 931. So, according to the property mentioned in Step 1, we have: $$e^{\ln 931} = 931$$ So, after evaluating the given expression, we find that $$e^{\ln 931} = 931$$.

Key Concepts

Natural Logarithms

When we talk about natural logarithms, we refer to a logarithm with a specific base: the mathematical constant \(e\). This constant is approximately equal to 2.718. The natural logarithm of a number, denoted as \(\ln\), is the power to which \(e\) must be raised to produce that number. In simpler terms:

• \(\ln(x)\) is the exponent \(y\) in the equation \(e^y = x\).

Natural logarithms are particularly useful in solving equations involving exponential growth or decay, such as compound interest or population growth scenarios. They provide a more straightforward way to handle these calculations mathematically.
Understanding natural logarithms allows us to convert multiplicative processes into additive ones, simplifying complex problems. Hence, they are a crucial tool in both mathematics and real-world applications.

Inverse Relationships

The concept of inverse relationships in mathematics is crucial for understanding natural logarithms and exponential functions. Two functions are inverses of each other if one function undoes the effect of the other. In terms of exponentials and logarithms:

• The exponential function \(e^x\) raises \(e\) to the power of \(x\).
• The natural logarithm \(\ln(x)\) is the power that \(e\) needs to be raised to get \(x\).
• Together, these functions undo each other's operations.

This relationship is expressed as \(e^{\ln(x)} = x\) and \(\ln(e^x) = x\). These properties highlight their inverse nature by showing how each function can "cancel out" the other's effects. Such understanding is pivotal in manipulating equations and solving problems efficiently in both theoretical and applied contexts.

Properties of Exponents

Understanding the properties of exponents is fundamental to solving many algebraic expressions and equations. These properties simplify complex expressions significantly, reducing potential errors:

• Product Property: \(a^m \cdot a^n = a^{m+n}\), which simplifies multiplication of powers with the same base.
• Quotient Property: \(\frac{a^m}{a^n} = a^{m-n}\), allowing division of powers with the same base.
• Power of a Power: \((a^m)^n = a^{m\cdot n}\), simplifying calculations when raising a power to another power.
• Zero Exponent: Any non-zero number raised to the power of zero is 1, \(a^0 = 1\).
• Negative Exponent: \(a^{-n} = \frac{1}{a^n}\), which inverts the base to a reciprocal.

Applying these properties allows you to change complex exponentiation expressions into simpler forms or expressions. When dealing with natural logarithms and exponential functions, these properties help in deriving relationships or transforming expressions to more manageable forms.