What's the coefficient of x^2 in the expansion of (2 - 1/2x)^4
(I've no idea hw to go bout this & I would also like to know under which topic it falls)
It falls under the binomial theorem or binomial expansion when there are finite terms (this case).
When the number of terms is infinite, such as
(2-x/2)^(-3), then it falls under Taylor's series.
Following are some typical references:
http://mathworld.wolfram.com/BinomialSeries.html
http://www.purplemath.com/modules/binomial.htm
http://tutorial.math.lamar.edu/Classes/CalcII/TaylorSeries.aspx