# Simplify This!

JS357
Posers and Puzzles 18 Jan '15 01:09
1. 18 Jan '15 01:09
Simplify the following exercise in multiplication as much as possible:

(x+a)(x-b)(x+c)(x-d)...(x-z)

2. 18 Jan '15 11:57
0
3. wolfgang59
19 Jan '15 07:38
Very good. Didn't get it straight away. π (Maths degree)
4. sonhouse
Fast and Curious
19 Jan '15 18:562 edits
Originally posted by wolfgang59
Very good. Didn't get it straight away. π (Maths degree)
Wouldn't that depend on a multiplication being a zero? I mean, what if X=28 and a=0, b =1, c=2, etc.? Where would there be a zero multiplicand result?
5. bbarr
Chief Justice
19 Jan '15 19:25
Originally posted by sonhouse
Wouldn't that depend on a multiplication being a zero? I mean, what if X=28 and a=0, b =1, c=2, etc.? Where would there be a zero multiplicand result?
One of the items in the series is (x-x)...
6. sonhouse
Fast and Curious
20 Jan '15 15:04
Originally posted by bbarr
One of the items in the series is (x-x)...
Yeah, that would do itπ
7. 20 Jan '15 23:40
except if x = +- infinity, when the answer is undefined
8. sonhouse
Fast and Curious
21 Jan '15 15:13
Originally posted by iamatiger
except if x = +- infinity, when the answer is undefined
Is infinity minus infinity undefined?
9. 21 Jan '15 19:22
Originally posted by iamatiger
except if x = +- infinity, when the answer is undefined
as x --> infinity, x - x = what?
10. Ponderable
chemist
21 Jan '15 19:32
Originally posted by iamatiger
except if x = +- infinity, when the answer is undefined
infinity is a symbol not a number, so x can't equal infinity...Even the lim(x->infinity) doesn't yield any kind of problem.
11. 23 Jan '15 00:343 edits
Infinity - Infinity is undefined, as with an infinite number of hotel rooms I can either put an infinite number of guests in every room, having zero free rooms, or I can put an infinite number of guests in every second room, having an infinite number of free rooms, or I can miss out any finite number of rooms at the start, and still fit my guests in with that finite number of rooms left.

I think claiming infinity is a symbol and not a number is rather dodgy. All numbers are symbols too, and infinity comes up in valid mathematics. If you are worried about saying x=infinity, then let us define x=1/0
12. 23 Jan '15 01:002 edits
Originally posted by iamatiger
Infinity - Infinity is undefined, as with an infinite number of hotel rooms I can either put an infinite number of guests in every room, having zero free rooms, or I can put an infinite number of guests in every second room, having an infinite number of free rooms, or I can miss out any finite number of rooms at the start, and still fit my guests in with t ...[text shortened]... es up in valid mathematics. If you are worried about saying x=infinity, then let us define x=1/0
So pretending, we have x = 1/0.

What is 1/0 - 1/0?

Multiply both sides by 0. Eliminates the 0's.

We have 1-1.*

What is 1-1?

0.

Ergo, x-x=0 even when x=1/0 in the pretend world.

*Edit: or we have 0-0 at the starred equation. Same outcome.
13. 24 Jan '15 08:58
π
multiplying both sides by 0 just proves 0=0 (as 0 converts everything to 0)

4 = 5
multiply both sides by 0
0 = 0

0/0 is undefined too, by the way
14. wolfgang59