Changing the subject of a formula

  • Thread starter chuckienz
  • Start date
  • #1
2
0

Main Question or Discussion Point

Ok, this most likely will be a silly question but im having trouble trying to make X the subject of the formula XA +BA = B

im hoping someone is able to enlighten me

Thanks
 

Answers and Replies

  • #2
  • #3
HallsofIvy
Science Advisor
Homework Helper
41,794
924
That British for what we Americans would call "solve the equation for x".

chuckienz, you solve an equation, or make x the subject of the equation, by "reversing" what has been done to x. Here, the equation is XA+ BA= B.

If I were given a value for A and asked to evaluate the left side, I would do two things: first multiply by A, second add BA. Here, you want to do the opposite. The opposite of "multiply by A" is "divide by A" or, same thing, "mutiply by A-1". The opposite of "add BA" is "subtract BA". Also, you because you are "reversing" everything you must also reverse the order. And, of course, anything you do to the left side of the equation, you must do to the right side.

So:
1) Subtract BA from both sides of the equation.
2) Multiply both sides of the equation by A-1.
 

Related Threads for: Changing the subject of a formula

  • Last Post
Replies
12
Views
18K
Replies
5
Views
2K
  • Last Post
Replies
1
Views
2K
Replies
1
Views
3K
Replies
3
Views
1K
Replies
4
Views
520
  • Last Post
Replies
11
Views
5K
Replies
49
Views
6K
Top