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

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)

??

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.

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.