/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 18 If \(\log _{3} 81=x-y\) and \(\l... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

If \(\log _{3} 81=x-y\) and \(\log _{2} 32=x+y\) determine the values of \(x\) and \(y\)

Short Answer

Expert verified
The values of \( x \) and \( y \) are \( \frac{9}{2} \) and \( \frac{1}{2} \), respectively.

Step by step solution

01

Convert Logarithmic Equations to Exponential Form

To solve the logarithmic equations, first convert them into exponential form. For \(\log _{3} 81=x-y\): \[ 3^{x-y} = 81 \] Since \ 81 = 3^4 \, we have \[ 3^{x-y} = 3^4 \] Therefore: \ x-y = 4 \
02

Convert the Second Logarithmic Equation to Exponential Form

Next, convert the second given logarithmic equation \( \log _{2} 32=x+y \): \[ 2^{x+y} = 32 \] Since \ 32 = 2^5 \, we have \[ 2^{x+y} = 2^5 \] Therefore: \ x+y = 5 \
03

Form a System of Linear Equations

Using the results from Steps 1 and 2, form a system of linear equations: \[ x - y = 4 \ x + y = 5 \]
04

Solve the System of Linear Equations

Add the two equations to eliminate \( y \): \[ (x - y) + (x + y) = 4 + 5 \] Simplify: \[ 2x = 9 \] Solve for \( x \): \[ x = \frac{9}{2} \]
05

Substitute \( x \) to find \( y \)

Use the value of \( x = \frac{9}{2} \) in one of the original equations. Substitute into \( x + y = 5 \): \[ \frac{9}{2} + y = 5 \] Solve for \( y \): \[ y = 5 - \frac{9}{2} \] \[ y = \frac{10}{2} - \frac{9}{2} \] \[ y = \frac{1}{2} \]

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

exponential form
To solve logarithmic equations, one useful method is converting them into their exponential form. This is because exponential equations are often simpler to manage. For instance, take the logarithmic equation \( \log_{3} 81 = x - y \). To convert it to exponential form, recall that the logarithm \( \log_b a = c \) implies \( \ b^c = a \). Thus, \( \log_{3} 81 = x - y \) becomes \( \ 3^{x - y} = 81 \).
Now, since 81 can be written as \( \ 3^4 \), we end up with \( \ 3^{x - y} = 3^4 \). Because the bases are the same (base 3), we can set the exponents equal to each other. Therefore, \( \ x - y = 4 \).
Similarly, for the second equation \( \log_{2} 32 = x + y \), we convert it to exponential form as \( \ 2^{x + y} = 32 \). Since \( \ 32 = 2^5 \), it translates to \( \ 2^{x + y} = 2^5 \). By setting the exponents equal to each other, we get \( \ x + y = 5 \).
Converting to exponential form thus simplifies logarithmic equations substantially, making subsequent steps more straightforward.
system of linear equations
After converting logarithmic equations to exponential form, you often arrive at simpler equations that can form a system of linear equations.
In our example, the converted equations are \( \ x - y = 4 \) and \( \ x + y = 5 \). These two equations together form a system of linear equations.
To solve such a system, you can use various methods:
  • **Substitution Method**: Solve one equation for one variable and substitute that in the other equation.
  • **Elimination Method**: Add or subtract equations to eliminate one variable, then solve for the other.
In this case, the elimination method is quite handy. By adding \( \ x - y \) and \( \ x + y \), the \( \ y \) terms cancel out, simplifying the process.
The added equation is \( \ 2x = 9 \), where solving for \( \ x \) gives \( \ x = \frac{9}{2} \).
To find \( \ y \), substitute \( \ x \) into one of the original equations: \( \ x + y = 5 \) becomes \( \ \frac{9}{2} + y = 5 \). Solving this provides \( \ y = \frac{1}{2} \).
solving logarithms
Solving logarithms involves converting them to forms that are easier to manage, usually exponential form, and employing algebraic methods.
Logarithms are the inverse operations of exponentiation. This means \( \ log_b(a) = c \) is the same as saying \( \ b^c = a \).
When solving logarithmic equations like \( \ log_{3} 81 = x - y \) and \( \ log_{2} 32 = x + y \), follow these steps:
  • **Convert to Exponential Form**: Make the equation linear by converting it so the bases and exponents can be compared directly.
  • **Simplify**: If the numbers are powers of the logarithm's base, simplify by equating exponents.
  • **Form Linear Equations**: Incorporate these simplified forms into linear equations to create a system of equations.
  • **Solve**: Use methods like elimination or substitution to solve the system of equations.
The combined approach of utilizing exponential forms and solving systems of equations allows you to break down complex logarithms into simpler parts. This step-by-step method is efficient and comprehensible when grappling with logarithmic problems.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

If \(\log _{5} x=2,\) then determine \(\log _{5} 125 x\).

If \(\log _{3} m=n,\) then determine \(\log _{3} m^{4},\) in terms of \(n\).

The German astronomer Johannes Kepler developed three major laws of planetary motion. His third law can be expressed by the equation \(\log T=\frac{3}{2} \log d-3.263\) where \(T\) is the time, in Earth years, for the planet to revolve around the sun and \(d\) is the average distance, in millions of kilometers, from the sun. a) Pluto is on average 5906 million kilometers from the sun. To the nearest Earth year, how long does it take Pluto to revolve around the sun? b) Mars revolves around the sun in 1.88 Earth years. How far is Mars from the sun, to the nearest million kilometers?

The apparent magnitude of a celestial object is how bright it appears from Earth. The absolute magnitude is its brightness as it would seem from a reference distance of 10 parsecs (pc). The difference between the apparent magnitude, \(m\), and the absolute magnitude, \(M,\) of a celestial object can be found using the equation \(m-M=5 \log d-5,\) where \(d\) is the distance to the celestial object, in parsecs. Sirius, the brightest star visible at night, has an apparent magnitude of -1.44 and an absolute magnitude of 1.45 a) How far is Sirius from Earth in parsecs? b) Given that \(1 \mathrm{pc}\) is approximately 3.26 light years, what is the distance in part a) in light years?

The formula for the Richter magnitude, \(M\) of an earthquake is \(M=\log \frac{A}{A_{0}},\) where \(A\) is the amplitude of the ground motion and \(A_{0}\) is the amplitude of a standard earthquake. In \(1985,\) an earthquake with magnitude 6.9 on the Richter scale was recorded in the Nahanni region of the Northwest Territories. The largest recorded earthquake in Saskatchewan occurred in 1982 near the town of Big Beaver. It had a magnitude of 3.9 on the Richter scale. How many times as great as the seismic shaking of the Saskatchewan earthquake was that of the Nahanni earthquake?

See all solutions

Recommended explanations on Math Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.