AnswersFL-1200330-Algebra 2 CREvaluating Logarithmic Expressions

Solving Logarithmic Equations using Technology Answers

23 verified answers3 views
21
Free Preview

Elsa tries to solve the following equation, and determines there is no solution. Is she correct? Explain. log2x = log2(3x + 5) + 4

Answer:

Elsa is correct; there is no solution. To solve the equation $\log_2(x) = \log_2(3x + 5) + 4$, first combine the logarithmic terms: $\log_2(x) - \log_2(3x + 5) = 4$, which simplifies to $\log_2(\frac{x}{3x + 5}) = 4$. Converting to exponential form gives $\frac{x}{3x + 5} = 2^4 = 16$. Solving for $x$: $x = 16(3x + 5) \implies x = 48x + 80 \implies -47x = 80 \implies x = -\frac{80}{47}$. However, in the original equation, the domain for $\log_2(x)$ requires $x > 0$. Since $x = -\frac{80}{47}$ is negative, it is an extraneous solution. Because this is the only potential solution, the equation has no real solution.

23

2.3219–0.4307–2.32190.4307

A
2.3219
B
–0.4307
C
–2.3219
D
0.4307
24

Did you include the following in your solution?

A
Identify the system of equations that can be graphed to solve the problem.
B
Use the change of base formula.
C
Determine that the graphs of the two equations do not intersect.
D
Determine that Elsa is correct; the equation has no solution.

Did you find these answers helpful?