How do you rearrange an equation with three unknown denominators?

  • Context: High School 
  • Thread starter Thread starter 4rfvgyhnjik
  • Start date Start date
  • Tags Tags
    Formulas
Click For Summary

Discussion Overview

The discussion revolves around the process of rearranging an equation with three unknown denominators, specifically focusing on the equation 1/a + 1/b = 1/c. Participants explore methods to isolate one variable, in this case, making b the subject of the formula. The scope includes mathematical reasoning and problem-solving strategies relevant to algebraic manipulation.

Discussion Character

  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant seeks clarification on how to rearrange the equation 1/a + 1/b = 1/c to solve for b.
  • Another participant suggests starting by multiplying both sides of the equation by the common denominator, abc, to find an equivalent equation.
  • A third participant provides a step-by-step rearrangement, showing that 1/b can be expressed as 1/c - 1/a, leading to b = 1/(1/c - 1/a).
  • Further simplification is proposed, resulting in b = ac/(a - c), with a note that the level of simplification required may depend on the specific application.
  • One participant endorses the approach of another, indicating that it is the easiest to generalize.

Areas of Agreement / Disagreement

Participants present multiple methods for rearranging the equation, and while there is agreement on the steps taken, there is no consensus on the necessity of simplification or the best approach to generalize the solution.

Contextual Notes

Some participants emphasize the importance of understanding properties of real numbers in the context of rearranging equations, but there are no explicit limitations or unresolved mathematical steps noted.

4rfvgyhnjik
Messages
1
Reaction score
0
just revising for gcse's and there always seems to be a question with three unknown denominators and you have to rearrange the equation

they are usually like
1/a+1/b=1/c
make b the subject of the formula
can you explain how to do this
 
Mathematics news on Phys.org
Based on your wording, what you want is not clear. Are you trying to solve the equation for b? You need to understand and know how to use the properties of real numbers. You will find an equation that is equivalent to your given one. I would start by multiplying both sides of the equation by the common denominator, abc.
 
1/a+1/b=1/c
1/b=1/c-1/a
b=1/(1/c-1/a)
 
If you want to continue to simplify it further:
b=1/(1/c-1/a)
b=ac/(a-c)

That is generally considered more simplified, but how simplified is necessary completely depends on the application.
 
simbolipoint's tip is best, because it is the easiest to generalize.

[tex] \begin{align*}<br /> \frac 1 a + \frac 1 b & = \frac 1 c \\<br /> abc\left(\frac 1 a + \frac 1 b\right) & = \frac{abc}{c} \\<br /> \frac{abc}{a} + \frac{abc}{b} & = ab \\<br /> bc + ac & = ab \\<br /> ac & = ab-bc = b(a-c)\\<br /> \frac{ac}{a-c} & = b <br /> \end{align*}[/tex]
 

Similar threads

  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 10 ·
Replies
10
Views
2K
Replies
9
Views
4K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 12 ·
Replies
12
Views
3K
  • · Replies 13 ·
Replies
13
Views
2K
  • · Replies 3 ·
Replies
3
Views
1K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K