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Adding & Subtracting Factors

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by stilite » Tue Sep 08, 2009 8:11 am
I have come across this problem,... and after trying to analyze the author's answer, I can't figure out how he came up with one "break-down" of it. Before I post the answer, could someone else try it and let me know how they came up with the answer and perhaps the best way to approach adding and subtracting factors?

Many thanks.
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by bharathh » Tue Sep 08, 2009 8:41 am
1/10^9 is common ... so factor it out.

1/10^9 - 1/10^10 = 1/10^9 (1-1/10) = 1/10^9 (9/10) = 9/10^10
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by stilite » Tue Sep 08, 2009 8:57 am
but I simply do not see where the "1" is coming from in the factoring.

How is the (1/10*9 x 1/10)

all of a sudden (1 - 1/10)

??
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by bharathh » Tue Sep 08, 2009 9:21 am
1/10^9 = 1*(1/10^9) correct?

So if I factor 1/10^9 out ... I am left with 1

Take an eqn x+2xy

If you factor out x you get x(1+2y)

It's the same thing. Don't let the reciprocal fool you.
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by stilite » Tue Sep 08, 2009 9:43 am
bharathh wrote:1/10^9 = 1*(1/10^9) correct?

So if I factor 1/10^9 out ... I am left with 1

Take an eqn x+2xy

If you factor out x you get x(1+2y)

It's the same thing. Don't let the reciprocal fool you.

Thank you,...I see now. What I didn't understand is that the factoring was at the first stage of the full (original) equation. The answer I have **see below** was throwing me off as it is not clearly laid out (in my opinion).

It looks like the author has not clearly shown the "factoring out" of the 1/10^9 in the second part...but in the third. His "second" factor of the answer should not even be there.
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