Math Problem Statement

log7 4π‘₯ ― log7(π‘₯ + 1) = 1 2 log7 4

Solution

We are tasked with solving the equation:

log⁑7(4x)βˆ’log⁑7(x+1)=1+2log⁑7(4).\log_7(4x) - \log_7(x + 1) = 1 + 2\log_7(4).

Step-by-step Solution

1. Simplify the right-hand side:

Using the logarithmic property alog⁑b(c)=log⁑b(ca)a\log_b(c) = \log_b(c^a), rewrite 2log⁑7(4)2\log_7(4) as: 2log⁑7(4)=log⁑7(42)=log⁑7(16).2\log_7(4) = \log_7(4^2) = \log_7(16). Thus, the equation becomes: log⁑7(4x)βˆ’log⁑7(x+1)=1+log⁑7(16).\log_7(4x) - \log_7(x + 1) = 1 + \log_7(16).

2. Combine terms on the right-hand side:

Using the property log⁑b(A)+log⁑b(B)=log⁑b(Aβ‹…B)\log_b(A) + \log_b(B) = \log_b(A \cdot B), rewrite 1+log⁑7(16)1 + \log_7(16) as: 1=log⁑7(7),∴1+log⁑7(16)=log⁑7(7β‹…16)=log⁑7(112).1 = \log_7(7), \quad \therefore 1 + \log_7(16) = \log_7(7 \cdot 16) = \log_7(112). Thus, the equation becomes: log⁑7(4x)βˆ’log⁑7(x+1)=log⁑7(112).\log_7(4x) - \log_7(x + 1) = \log_7(112).

3. Simplify the left-hand side:

Using the property log⁑b(A)βˆ’log⁑b(B)=log⁑b(AB)\log_b(A) - \log_b(B) = \log_b\left(\frac{A}{B}\right), rewrite the left-hand side as: log⁑7(4xx+1).\log_7\left(\frac{4x}{x + 1}\right). Thus, the equation is now: log⁑7(4xx+1)=log⁑7(112).\log_7\left(\frac{4x}{x + 1}\right) = \log_7(112).

4. Remove the logarithms:

Since the equation log⁑b(A)=log⁑b(B)\log_b(A) = \log_b(B) implies A=BA = B, we get: 4xx+1=112.\frac{4x}{x + 1} = 112.

5. Solve for xx:

Multiply through by x+1x + 1 (assuming xβ‰ βˆ’1x \neq -1): 4x=112(x+1).4x = 112(x + 1). Expand the right-hand side: 4x=112x+112.4x = 112x + 112. Rearrange terms: 4xβˆ’112x=112β€…β€ŠβŸΉβ€…β€Šβˆ’108x=112.4x - 112x = 112 \quad \implies \quad -108x = 112. Solve for xx: x=βˆ’112108=βˆ’2827.x = -\frac{112}{108} = -\frac{28}{27}.

6. Verify the solution:

Since log⁑(x)\log(x) is undefined for non-positive xx, the solution x=βˆ’2827x = -\frac{28}{27} is not valid.

Conclusion:

There is no solution to the given equation.


Do you have questions about any part of the solution, or would you like further clarification?

Relative Questions:

  1. What are the properties of logarithms used in this problem?
  2. Can logarithmic equations have no solution, and why?
  3. How does the domain of logarithmic functions affect solutions?
  4. What would happen if xx had been positive in this case?
  5. How can you graphically check for solutions to this equation?

Tip:

Always verify the domain of the logarithmic terms to ensure the solutions are valid within the equation's constraints!

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Math Problem Analysis

Mathematical Concepts

Logarithms
Properties of Logarithms
Equations

Formulas

log_b(A) - log_b(B) = log_b(A / B)
a * log_b(C) = log_b(C^a)
log_b(A) + log_b(B) = log_b(A * B)

Theorems

Logarithmic Equality Theorem: If log_b(A) = log_b(B), then A = B

Suitable Grade Level

Grades 10-12