Mathematics Grade 11 15 min

Convert between exponential and logarithmic form: rational bases

Convert between exponential and logarithmic form: rational bases

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1

Introduction & Learning Objectives

Learning Objectives Define the relationship between exponential and logarithmic forms. Correctly identify the base, argument, and exponent in both exponential and logarithmic equations with rational bases. Convert an exponential equation with a rational base into its equivalent logarithmic form. Convert a logarithmic equation with a rational base into its equivalent exponential form. Solve for an unknown variable in a simple logarithmic equation by converting it to exponential form. Evaluate simple logarithmic expressions involving rational bases and negative exponents. Ever wondered how to solve for an exponent when the base is a fraction, like (1/2)^x = 8? 🤔 Logarithms are the key to unlocking these types of problems! This tutorial will teach you the fundamental relation...
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Key Concepts & Vocabulary

TermDefinitionExample Exponential FormAn equation written in the form b^x = a, where 'b' is the base, 'x' is the exponent, and 'a' is the result or argument.In (1/2)^3 = 1/8, the base is 1/2, the exponent is 3, and the result is 1/8. Logarithmic FormAn equation written in the form log_b(a) = x, which is the inverse of the exponential form. It asks, 'To what power must we raise the base 'b' to get the argument 'a'?'log_{1/2}(1/8) = 3 is the logarithmic equivalent of (1/2)^3 = 1/8. Base (b)The number being raised to a power in exponential form, or the subscript in logarithmic form. For logarithms, the base must be a positive number not equal to 1.In the equation log_{2/3}(4/9) = 2, the base is the rational number 2/3. Argument (a)T...
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Core Formulas

The Fundamental Conversion Rule b^x = a <=> log_b(a) = x This is the core principle for converting between the two forms. To use it, identify the base (b), the exponent (x), and the argument (a). The base of the exponent is always the base of the logarithm. The exponent always becomes the answer of the logarithm. Negative Exponent Rule for Rational Bases (p/q)^-n = (q/p)^n This rule is essential when working with rational bases and negative exponents. A negative exponent indicates you should take the reciprocal (flip) of the fractional base and then apply the positive exponent. This is frequently needed when converting or evaluating logarithms.

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Sample Practice Questions

Challenging
Evaluate the expression: log_{9/4}(log_{1/3}(1/27))
A.3/2
B.2/3
C.1/2
D.-1/2
Challenging
Solve for x: log_{x/(x-1)}(9/4) = 2. Assume x > 1.
A.3/2
B.3
C.2
D.5/2
Challenging
If log_{1/2}(a) = 4 and log_b(1/81) = -2, what is the value of log_b(a)?
A.2/9
B.2
C.-2
D.1/2

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