Math Is Fun Forum

PatternMan

Member

Registered: 2014-03-08

Posts: 199

A little confusion

Is there a problem in my calculation multiplying those brackets? Also why are they allowed to switch those terms? Actually I just realized I think. Is it because a + b = -a -b ? I really need to master the basics first. (－‸ლ)

Last edited by PatternMan (2014-08-26 11:01:51)

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"School conditions you to reject your own judgement and experiences. The facts are in the textbook. Memorize and follow the rules. What they don't tell you is the people that discovered the facts and wrote the textbooks are people like you and me."

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: A little confusion

Hi PatternMan

because

.

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“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

PatternMan

Member

Registered: 2014-03-08

Posts: 199

Re: A little confusion

Hi PatternMan

because

.

I think I may have missed something. I didn't know you could do that. Is there a name for this? I don't remember learning that the order of terms in an absolute value can be switched.

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"School conditions you to reject your own judgement and experiences. The facts are in the textbook. Memorize and follow the rules. What they don't tell you is the people that discovered the facts and wrote the textbooks are people like you and me."

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: A little confusion

Since the Abs value operator only takes the positive answer...

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: A little confusion

Hi PatternMan

Do you remember how the absolute value of a number is defined?

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“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

PatternMan

Member

Registered: 2014-03-08

Posts: 199

Re: A little confusion

Hi PatternMan

Do you remember how the absolute value of a number is defined?

I just wrote

|9-5-3| = |5-9-3| = 6 I don't know why that works but it works for those values anyway. Also I just learnt that the absolute value was the displacement from the origin or 0.

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"School conditions you to reject your own judgement and experiences. The facts are in the textbook. Memorize and follow the rules. What they don't tell you is the people that discovered the facts and wrote the textbooks are people like you and me."

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: A little confusion

Horrible definitions of math books.

For numbers it is always the positive value.

When you switch the subtraction of two numbers you change the sign.

a - b = - ( b - a )

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

PatternMan

Member

Registered: 2014-03-08

Posts: 199

Re: A little confusion

Horrible definitions of math books.

For numbers it is always the positive value.

When you switch the subtraction of two numbers you change the sign.

a - b = - ( b - a )

I hope I understand it. I did skim over this stuff in one of the books Shivam suggested.

a + (-a) = 0
a = -(-a)
-b = -b,
a - b = -b - (- a) =  -(b - a)

Last edited by PatternMan (2014-08-27 09:00:25)

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"School conditions you to reject your own judgement and experiences. The facts are in the textbook. Memorize and follow the rules. What they don't tell you is the people that discovered the facts and wrote the textbooks are people like you and me."