Changing the subject of a formula

  • Thread starter chuckienz
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In summary, to make X the subject of the formula XA + BA = B, you need to subtract BA from both sides and then multiply both sides by A-1.
  • #1
chuckienz
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Ok, this most likely will be a silly question but I am having trouble trying to make X the subject of the formula XA +BA = B

im hoping someone is able to enlighten me

Thanks
 
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  • #2
chuckienz said:
make X the subject

What do you mean by "subject"?
 
  • #3
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.
 

FAQ: Changing the subject of a formula

How do you change the subject of a formula?

To change the subject of a formula, you need to isolate the variable that you want to make the subject. This is usually done by using algebraic techniques such as inverse operations, factoring, and substitution.

Why is it important to know how to change the subject of a formula?

Changing the subject of a formula allows us to solve for different variables and manipulate equations to better understand the relationships between different quantities. It is a fundamental skill in mathematics and is commonly used in many scientific fields.

What are the common steps involved in changing the subject of a formula?

The common steps involved in changing the subject of a formula include identifying the variable you want to make the subject, using inverse operations to isolate the variable, and simplifying the equation to get the desired variable on one side and all other terms on the other side.

Can changing the subject of a formula change the meaning of the equation?

No, changing the subject of a formula does not change the meaning of the equation. It only rearranges the terms to solve for a different variable. The equation will still represent the same relationship between the quantities involved.

Are there any limitations to changing the subject of a formula?

Yes, there are some limitations to changing the subject of a formula. The equation must be solvable and have a unique solution for the variable you want to make the subject. In some cases, it may not be possible to isolate the desired variable without making assumptions or using approximations.

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