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2017-05-06 12:01:16
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twp
Peasant
 
In math, we don't have an operation named "get rid of". You may (should) use one or more of the four math operators (add, subtract, multiply, divide) IN THAT ORDER. This is known as the order of precedence. Yes, you can and should look this up in any math text.

How do you know that you have an error in your analysis? Try doing an operation OUT OF ORDER.

For instance, try to divide first:

If you wish to ATTEMPT to remove the term a+b-c from both sides of the equation, you could (incorrectly) try to do a divide operation on both sides:

4(a+b-c)/(a+b-c) = 3(a+b-c)/(a+b-c)

However you are then dividing by zero... This gives an undefined result (look it up in any math text).

Attempting to divide by zero is an easy warning flag for any math operation.

The solution is to go back to initial conditions and first reduce them using the four operators (+-*/).

You already know that a+b-c = 0. You may substitute this known relation into the first equation. See my previous post.

4(a+b-c) = 3(a+b-c) where a+b-c = 0

4(0) = 3(0)

0 = 0

The apparent result (4=3) of your original analysis should raise a warning flag that one of your previous assumptions or operations was incorrect (not wrong, just not in the correct order of precedence). So you go back and look at each assumption to find the incorrect step.

What you are attempting to do, in this problem, is known as Simultaneous Solution of Equations. Again, look it up in your math texts.