# Changing subject of formula

• Mar 15th 2009, 03:05 AM
200001
Changing subject of formula
Hello
When changing the subject of a formula with roots and exponenets is the order of operations as follows?

divide/multiply
roots
powers

• Mar 15th 2009, 03:08 AM
Air
Quote:

Originally Posted by 200001
Hello
When changing the subject of a formula with roots and exponenets is the order of operations as follows?

divide/multiply
roots
powers

BODMAS: Brackets, Others (E.G. Indices, Square Root), Division, Multiplication, Addition, Subtraction.
• Mar 15th 2009, 08:32 AM
HallsofIvy
That is the "order of operations" when you are performing a calculation.

When you are solving an equation, you have to remember that you are "backing" out so everything runs in reverse.

For example, if $\displaystyle y=\frac{2x-1}{3}$ and had to calculate y for a given value of x (you know x and want to find y), you would use "BODMAS" or "PEMDAS" (P for parentheses instead of B for brackets- which you can remember as "Please excuse my dear aunt Sally"). Since the "vinculum" (the line between numerator and denominator) counts as a "bracket" or "parentheses" you first MULTIPLY 2 by x, the SUBTRACT 1, finally DIVIDE by 3.

But when you want to solve the equation- you know y and want to find x, just the opposite of the above- you do the opposite; the opposite of each operation in the opposite order. First you MULTIPLY both sides of the equation by 3 then ADD 1 to both sides, finally DIVIDE both sides by 2.
• Mar 16th 2009, 09:22 AM
200001
Thanks to both of you for the responses
I shall have a try