Question

Difficulty: EasyLogarithmic and Exponential Expressions and Equations

If log5x=3\log_5 x = 3, what is the value of xx?

  1. A
    8
  2. B
    15
  3. C
    25
  4. 125Answer
  5. E
    243

Answer

125
To solve the logarithmic equation log5x=3\log_5 x = 3, we apply the fundamental definition of a logarithm. A logarithmic equation of the form logbx=y\log_b x = y can be rewritten in exponential form as by=xb^y = x. In this equation, the base bb is 5 and the exponent yy is 3. Rewriting gives 53=x5^3 = x. Evaluating 535^3 yields 5×5×5=1255 \times 5 \times 5 = 125. Therefore, the correct value of xx is 125.

Step-by-Step Solution

1
Apply the definition of a logarithm to rewrite the logarithmic equation in its equivalent exponential form.
53=x5^3 = x
By definition, logbx=y\log_b x = y is equivalent to by=xb^y = x, where bb is the base, yy is the exponent, and xx is the argument.
2
Evaluate the exponential expression 535^3 to solve for xx.
x=125x = 125
Cubing 5 means multiplying it by itself three times: 5×5×5=1255 \times 5 \times 5 = 125.

Key Concept

Definition of Logarithms
Rate this question