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Here's the question:
assume x^2+3x+2=0
this factors to
(x+2)(x+1)=0

Now divide both sides by
(x+2)(X+1),
and you get

((x+2)(X+1))/((x+2)(X+1))=0/((x+2)(X+1))
For the left side, you get (x+2)(X+1) over itself, which is one, while for the right, since you are dividing 0, you get zero. This leaves you with:
1=0, which is obviously not right, where is the mistake in this problem?

2006-10-12 19:23:09 · 7 answers · asked by aglon314 2 in Science & Mathematics Mathematics

7 answers

Since (x+2)(x+1)=0, you can't divide by (x+1)(x+2), because you'd be dividing by zero.

2006-10-12 19:28:34 · answer #1 · answered by James L 5 · 0 0

You have already pointed out your mistake in this question.
You stated,

(x + 2)(x + 1) = 0

Now, if you divide both sides by (x + 2)(x + 1), this means you are actually dividing the entire equation by 0. Now, anything that has a denominator of 0 is undefined and it cannot be done.

2006-10-12 20:09:03 · answer #2 · answered by xxmizuraxx 2 · 0 0

The solutions are x=1 and x=2 either of which makes the right side=0. You have assumed that o/o=1but 0/0=0

2006-10-12 19:32:37 · answer #3 · answered by Anonymous · 0 0

The mistake is that for your polynomial to equal zero, then x must equal -2 or -1, in which case it already is zero. So what you're really doing is dividing zero by zero, which as you'll see in calculus has infinite solutions.

2006-10-12 19:27:24 · answer #4 · answered by ohmneo 3 · 1 0

(x+2)(x+1) is already equal to 0
you cannot again divide it by by (x+2)(X+1) cause it would be like ur dividing by 0 again

2006-10-12 20:44:37 · answer #5 · answered by confused 2 · 0 0

It's just the same as if you said:

a = 0

Divide both sides by a:
a/a = 0
1 = 0

As others have noted, you are dividing by zero and that is not allowed!

2006-10-12 19:31:36 · answer #6 · answered by Puzzling 7 · 0 0

Dividing by zero is not a defined operation, regardless of the numerator.

2006-10-12 19:28:26 · answer #7 · answered by Frank N 7 · 0 0

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