The Impossible Factorisation

**Bench.** · September 9th 2009, 07:02 AM

My friend and I are arguing again, about Maths (How cool are we?).

Please, just assure me (and him), that you cannot factorise the equation:

$x^2 + 100$

So that there are two brackets, each with a value of $x$ in.

**Wilmer** · September 9th 2009, 07:15 AM

Originally Posted by Bench.

Please, just assure me (and him), that you cannot factorise the equation:
$x^2 + 100$

That's not an equation. ALL equations have an = sign.

(x+10)(x+10) - 20x

**red_dog** · September 9th 2009, 07:16 AM

It can't be factorized over $\mathbb{R}$ , but it can be factorized over $\mathbb{C}$ :

$x^2+100=(x-10i)(x+10i)$

**Bench.** · September 9th 2009, 09:38 AM

Originally Posted by red_dog

It can't be factorized over $\mathbb{R}$ , but it can be factorized over $\mathbb{C}$ :

$x^2+100=(x-10i)(x+10i)$

What is factorising over "C"?

**Pim** · September 9th 2009, 09:42 AM

R is the set of numbers you encounter in everyday life. This includes whole numbers, fractions and numbers like Pi. C is the set of all those and the complex numbers, which includes i, the root of -1.

**Bench.** · September 9th 2009, 09:54 AM

Fantastic. What does C and R stand for, if they stand for anything?

**Pim** · September 9th 2009, 09:59 AM

C stands for Complex, R for Real. (I think)

**aidan** · September 9th 2009, 12:41 PM

Originally Posted by Bench.

Fantastic. What does C and R stand for, if they stand for anything?

You may want to do a search:

N - natural numbers

Z - integers

Q - rational numbers

R - real numbers

C - complex numbers

Its important to know what each set includes and its properties.

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