Understanding Algebraic Expressions: Simplifying Subtraction as Addition

[Holocene]

I will use this expression as an example:

-2x + 7y - 5

Now, I know that this expression literally means " negative 2x plus 7y minus 5".

But, I prefer to look an expression like this as simply the sum of 3 terms. The terms are: -2x, 7y, and -5.

So, I prefer to deal with the expression more like -2x + 7y + (-5)

Is this proper?

 

[mathman]

It is proper, but what's the point?

 

[HallsofIvy]

There are many different ways of looking at any "expression"- mathematics or not.

 

[CRGreathouse]

That is proper and sometimes useful. Looking at the same thing different waysis a good skill to have for math.

 

[Math Jeans]

Its proper as long as it doesn't change the value.

 

[Holocene]

It is proper, but what's the point?

 

[MarineMef07]

I agree with mathman, it's right but you're just complicating everything. In math the best way to do it is to follow the rules or you'll just end up completely confused...

 

[HallsofIvy]

It is proper, but what's the point?

Since addition is associative and subtraction is not, many algebraist do not look upon subtraction as properly an operation at all- subtraction just means "add the negative". To such mathematicians, the sum
(-2x) + 7y + (-5) would be much more natural than "subtracting 5".

 

[CRGreathouse]

Since addition is associative and subtraction is not, many algebraist do not look upon subtraction as properly an operation at all- subtraction just means "add the negative". To such mathematicians, the sum
(-2x) + 7y + (-5) would be much more natural than "subtracting 5".

I feel that way myself. In fact, I would go so far as to say that the subtraction symbol is just a shorthand for "add the negation".