# Math Help - binomial expansion

1. ## binomial expansion

i have to find the first 4 terms of the expansion of
(1-0.5x)^0.5
i have to have it in the form (1+x)^n before i can do it don't i? but i cant remember how to do this! any help would be appreciated!

2. Originally Posted by Oranges&Lemons
i have to find the first 4 terms of the expansion of
(1-0.5x)^0.5
i have to have it in the form (1+x)^n before i can do it don't i? but i cant remember how to do this! any help would be appreciated!
done it dont worry

3. ## The general binomial series

The general binomial coeffeint where $\alpha$ is not a natural number is

${\alpha\choose{k}}:=\frac{\alpha(\alpha-1)...(\alpha-k+1)}{k!})$ if $k \ne 0$

$1+\alpha x+\frac{\alpha(\alpha-1)}{2!}x^2+\frac{\alpha(\alpha-1)(\alpha-2)}{3!}x^3$

4. Use {{\alpha}\choose k}

5. Or by writting &#091;math]\binom\alpha k[/tex] yields the same.