High School

h. log_5 x = log_5(2x+3) - log_5(3x + 1)

5. Express

a. 2log_{10} a - (1/3)log_{10} b + 2 as a single logarithm

b. log_c(x+1) - log_c(x-1) + A as a single logarithm, where A = log_c B.

Answer :

Let's solve the given problems step-by-step. We will express each expression as a single logarithm using logarithmic properties.

a. Express [tex]2\log_{10} a - \frac{1}{3}\log_{10} b + 2[/tex] as a single logarithm.

To express this as a single logarithm, we'll use the properties of logarithms:

  1. Power Rule: [tex]k\log_b M = \log_b M^k[/tex]
  2. Product Rule: [tex]\log_b M + \log_b N = \log_b (MN)[/tex]
  3. Quotient Rule: [tex]\log_b M - \log_b N = \log_b \left(\frac{M}{N}\right)[/tex]

Let's apply these properties step-by-step:

  1. Apply the Power Rule to each term:

    • [tex]2\log_{10} a = \log_{10} (a^2)[/tex]
    • [tex]\frac{1}{3}\log_{10} b = \log_{10} (b^{1/3})[/tex]
  2. This makes the expression:
    [tex]\log_{10} (a^2) - \log_{10} (b^{1/3}) + 2[/tex]

  3. The constant 2 needs to be expressed in terms of a logarithm base 10. We note that:
    [tex]2 = \log_{10}(10^2) = \log_{10} (100)[/tex]

  4. Combine all terms using the Product and Quotient Rules:
    [tex]\log_{10} \left(\frac{a^2 \cdot 100}{b^{1/3}}\right)[/tex]

Thus, the expression as a single logarithm is:
[tex]\log_{10} \left(\frac{100a^2}{b^{1/3}}\right)[/tex]

b. Express [tex]\log_c(x+1) - \log_c(x-1) + A[/tex] as a single logarithm, where [tex]A = \log_c B[/tex].

Let's follow the same logarithmic rules to simplify this expression:

  1. Substitute [tex]A = \log_c B[/tex] into the expression:
    [tex]\log_c(x+1) - \log_c(x-1) + \log_c B[/tex]

  2. Apply the Quotient Rule to [tex]\log_c(x+1) - \log_c(x-1)[/tex]:
    [tex]\log_c \left(\frac{x+1}{x-1}\right)[/tex]

  3. Combine with [tex]\log_c B[/tex] using the Product Rule:
    [tex]\log_c \left(\frac{x+1}{x-1} \cdot B\right)[/tex]

Thus, the expression as a single logarithm is:
[tex]\log_c \left(\frac{B(x+1)}{x-1}\right)[/tex]