so sánh A và B :
a) A = \(\frac{20}{39}+\frac{22}{27}+\frac{18}{43}\) ; B = \(\frac{14}{39}+\frac{22}{29}+\frac{18}{41}\)
b) A = \(\frac{3}{8^3}+\frac{7}{8^4}\) , B= \(\frac{7}{8^3}+\frac{3}{8^4}\)
c) A = \(\frac{10^7+5}{10^7-8}\) , B = \(\frac{10^8+6}{10^8-7}\)
d) A = \(\frac{10^{1992}+1}{10^{1991}+1}\), B = \(\frac{10^{1933}+1}{10^{1992}+1}\)