the break down of a negative binomial equation

**mcanski** · Jun19-09, 10:54 AM

Firstly, I want to note I'm a post college student who is attempting to teach himself calculus. I'm reading Calculus Made Easy by Silvanus P. Thompson and Martin Gardner, St. Martin's Press, 1998 ed.

My question comes from page 56 Case of a Negative Exponent

y + dy= (x + dx)^-2

= x^-2(1 + dx/x)^-2

I don't understand how the author got from (x + dx)^-2 to the answer x^-2(1 + dx/x)^-2

If someone could either breakdown the process, show me where to go and see examples of how this process is done, or point me in the direction to what emphasis of math I should read to better learn the process I will be grateful. Any help will be appreciated.

**Cyosis** · Jun19-09, 11:15 AM

Try to take it from here:

$LaTeX Code: <BR>(x+dx)^{-2}=\\left(\\frac{x}{x}(x+dx)\\right)^{-2}<BR>$

Realize that x/x is just 1 for x!=0 so you can put it in there without changing the expression.