a) cho $P=1-\frac{1}{2}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{2011}-\frac{1}{2012}$
$Q=\frac{1}{1007}+\frac{1}{1008}+...+\frac{1}{2012}$
tính P:Q?
b)Cho $M=\frac{1}{2}-\frac{3}{4}+\frac{4}{5}-...+\frac{197}{198}-\frac{199}{200} $
$N=\frac{1}{51}+\frac{1}{52}+...+\frac{1}{100}$
tính N:M?
c)tính $B=\frac{(1+\dfrac{2012}{1})(1+\dfrac{2012}{2})...(1+\dfrac{2012}{1000})}{(1+\dfrac{1000}{1})(1+\dfrac{1000}{2})...(1+\dfrac{1000}{2012})}$