chứng minh rằng:
a.\(\frac{1}{2^2}\)+\(\frac{1}{3^2}\)+\(\frac{1}{4^2}\).....+\(\frac{1}{2010^2}\)<1
b.\(\frac{1}{4}\)+\(\frac{1}{16}\)+\(\frac{1}{36}\)+\(\frac{1}{64}\)+\(\frac{1}{100}\)+\(\frac{1}{196}\)<\(\frac{1}{2}\)
c.\(\frac{2009^{2008}-1}{2009^{2009}-1}< \frac{2009^{2007}+1}{2009^{2008}+1}\)