Question regarding trinomial expansion

1. Apr 12, 2013

Hectorreturns

The co-efficient of t2 in the expansion of given equation is : (t<<1)

(1 - 2tw + t2)-1/2

I have never expanded trinomials with negative exponents. In the absence of w, it could be expanded with binomial theorem but with w I don't understand how to solve it.

2. Apr 12, 2013

Ray Vickson

I don't see anything with an '=' sign in it, so I don't see an equation. However, I do see an *expression*.

Anyway, do you know how to find the coefficients of $x^0 = 1$, $x^1$ and $x^2$ in the expansion of $f(x) = (1 - x)^{-1/2}?$ If so, just set $x = 2wt - t^2.$

3. Apr 12, 2013

Hectorreturns

Yeah *expression* instead of equation and thanks for the tip.