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Simplifying expressions
kimd6746
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How do you simplify the following equation?

(3x^2(x-2) - x + 2) / x - 2 = ?

Why am I not allowed to cancel the denominator by multiplying both sides by x-2? Even if I don't cancel out the denominator and try to combine the numerator, I get:

3x^3 - 6x^2 -x + 2 / x - 2

The trail stops cold there. What am I missing?
Re: Simplifying expressions
Guest



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kimd6746 wrote:
How do you simplify the following equation?

(3x^2(x-2) - x + 2) / x - 2 = ?

Why am I not allowed to cancel the denominator by multiplying both sides by x-2? Even if I don't cancel out the denominator and try to combine the numerator, I get:

3x^3 - 6x^2 -x + 2 / x - 2

The trail stops cold there. What am I missing?


You can't cancel out x-2 because it's part of the expression (3x^2(x-2) - x + 2). You can only cancel out if x-2 was a multiplier of the full expression.
Rey Fernandez
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Joined: 06 Mar 2007
Posts: 321

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Guest makes a good point. What's not immediately apparent, though, is that (x-2) *is* a factor of the numerator. You just have to massage it a little:

[3(x^2)*(x-2) - x + 2] / (x - 2) (I changed the notation a little for clarity)
[3(x^2)*(x-2) - (x - 2)] / (x - 2)
[(x - 2) [3(x^2) - 1] / (x - 2)
This is the tricky step. factor out (x-2) from both terms of the numerator, leaving behind two terms: 3(x^2) and -1, or [3(x^2) - 1]. Now, there's a (x - 2) factor in the numerator and the denominator, so cancel.

3(x^2) - 1


Rey
Simplifying expressions
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