Simple square root question

\sqrt{(\pm \hspace{0.1cm} x)^2} = \pm \hspace{0.1cm}x \hspace{0.1cm}

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Reply 1

TenOfThem

Original post by John taylor

\sqrt{(\pm \hspace{0.1cm} x)^2} = \pm \hspace{0.1cm}x \hspace{0.1cm}

No

It is |x|

(edited 10 years ago)

Reply 2

Munrot07

I think you are right :smile:

Try a number...2 2^2 = 4 and the square root of 4 is +/- 2

Try the negative...-2 -2^2 = 4 and the square root of 4 is +/- 2 so yes you are right :smile:

Reply 3

TenOfThem

Original post by Munrot07

I think you are right :smile:

Try a number...2 2^2 = 4 and the square root of 4 is +/- 2

Try the negative...-2 -2^2 = 4 and the square root of 4 is +/- 2 so yes you are right :smile:

No, he is not correct and neither are you

\sqrt{4} = 2

It does not = -2

Reply 4

Munrot07

Original post by TenOfThem

No, he is not correct and neither are you

\sqrt{4} = 2

It does not = -2

um what? you do know that the square root of a number is +/- the number...if you square a negative number you get a positive number -2^2 = 4, square rooting is the opposite so yes it can be negative...this is really simple maths...look it up online

http://answers.yahoo.com/question/index?qid=20081231145658AAdZ2yi

Reply 5

TenOfThem

Original post by Munrot07

um what? you do know that the square root of a number is +/- the number...if you square a negative number you get a positive number -2^ = 2, square rooting is the opposite so yes it can be negative...this is really simple maths...look it up online

No, you are still mistaken

Whilst

(-2)^2 = 4

as you said

By definition

\sqrt{4} = 2

and only 2

Reply 6

TenOfThem

Original post by Munrot07

Ahhhhh - I see you have linked to a post where some people know the answer and some people do not

(edited 10 years ago)

Original post by TenOfThem

No, you are still mistaken

Whilst

(-2)^2 = 4

as you said

By definition

\sqrt{4} = 2

and only 2

it really isn't...please look it up... the square root of a number can equal the negative, if you do A level maths in mark schemes any time you square root something you have to go the positive and the negative answer, seriously the square root of 4 can be -2

Reply 9

Phteven

Original post by Munrot07

Yahoo Answers isn't a reliable source for backing up incorrect claims :tongue:

Reply 10

TenOfThem

Original post by Munrot07

I could "look it up" if I needed too

You are under a very common mis-conception

Reply 11

Munrot07

Original post by StephenNaulls

Yahoo Answers isn't a reliable source for backing up incorrect claims :tongue:

It was the first one i found :P

here is wiki which says the same as what I am saying

http://en.wikipedia.org/wiki/Square_root

Reply 12

Munrot07

Original post by TenOfThem

I could "look it up" if I needed too

You are under a very common mis-conception

The thing is i'm not...look at the wiki link i just sent where it says " For example, 4 and −4 are square roots of 16 because 4² = (−4)² = 16."

Reply 13

Felix Felicis

Original post by Munrot07

No, by definition,

\sqrt{x^2} = |x|

Reply 14

TenOfThem

Original post by Munrot07

It was the first one i found :P

here is wiki which says the same as what I am saying

http://en.wikipedia.org/wiki/Square_root

That link does not agree with you

It correctly states

Every non-negative real number a has a unique non-negative square root, called the principal square root, which is denoted by √a, where √ is called the radical sign or radix. For example, the principal square root of 9 is 3, denoted √9 = 3, because 32 = 3 × 3 = 9 and 3 is non-negative

Reply 15

Forum User

Original post by Munrot07

The thing is i'm not...look at the wiki link i just sent where it says " For example, 4 and −4 are square roots of 16 because 4² = (−4)² = 16."

The article backs up what TenOfThem is saying.

He did not claim that -2 is not a square root of 4. He claimed that √4 = 2, and 2 only. √ is the positive square root, by definition.

Every positive number a has two square roots: √a, which is positive, and −√a, which is negative

(edited 10 years ago)

Reply 16

TenOfThem

Original post by Munrot07

The thing is i'm not...look at the wiki link i just sent where it says " For example, 4 and −4 are square roots of 16 because 4² = (−4)² = 16."

You are confusing 2 concepts

\sqrt{4} = 2

by definition

Reply 17

Dalek1099

Original post by TenOfThem

No

It is x

I thought sqrt((+-x)^2)=sqrt(x^2)=modulusx=+-x :confused:

As for the source that sqrt(x) only calculates the postive root:http://www.edexcel.com/migrationdocuments/GCE%20New%20GCE/UA035243_GCE_Lin_Maths_Issue_3.pdf

(edited 10 years ago)

Reply 18

Munrot07

Original post by Forum User

The article backs up what TenOfThem is saying.

it clearly says the root of a number has a positive and a negative...it doesn't matter if it is the "principle square root" a negative number can still be a square root...