The document provides examples and techniques for changing the subject of a formula. It demonstrates flipping both sides of an equation, multiplying or dividing both sides by the same term, and isolating the term to be made the subject by collecting like terms on one side of the equation and leaving the term by itself on the other side. Common mistakes discussed include incorrectly flipping terms individually rather than both sides of the equation and prematurely making denominators the same.

1. 4048 2EM Algebra – Change Subject (1) Math Academy®
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stored in any retrieval system of any nature without prior permission.
Math Academy® 1
Knowing is not enough; we must apply. Willing is not enough; we must do.
Johann Wolfgang von Goethe
Notes: Changing Subject of a Formula
Example 1: Make the letter in the brackets the subject of the given formula.
Example 2:
Example 3:
(3 )
2
w
x y c+ = ( )x
z
yx
m
=
-
( )y
1x y
m z
-
=
m
x y
z
- =
m
x y
z
- =
2
a
b c
x
= + ( )x
2 1
a b c
x
+
=
2 1x
a b c
=
+
2
a
x
b c
=
+
2( )
a
x
b c
=
+
Common mistake
m m
z
x y
- =
FLIP EACH side
Multiply on both sidesm
ALONEy
LHS and RHS one term each
FLIP EACH side (not flip individually)
Multiply on both sidesa
Common mistake
1 1
2
x
a b c
= +
LHS: ALONEx
Technique:
Flip

2. 4048 2EM Algebra – Change Subject (1) Math Academy®
All rights reserved. No part of this document may be reproduced or transmitted in any form or by any means, or
stored in any retrieval system of any nature without prior permission.
Math Academy® 2
Example 4:
Example 5:
Example 6:
3 2x y k
k y
-
= ( )x
2
R r
T
r
+
=
-
( )r
1
11
=+
ba
( )b
1 1
1
b a
= -
1 1a
b a a
= -
1 1a
b a
-
=
1 1
b a
a
=
-
1
a
b
a
=
-
appears oncex Do not Cross-multiply
appears twicer Cross-multiply
Group terms with r
Cross- Multiply
Factorise r
Make the term containing
on one side.b
Make Same Denominator
Flip
Do not make same denominator
at this stage (else appear
everywhere --- Tedious !!)
b