a) A=1998.1998
B=1996.2000=(1998-2)(1998+2)=1998.1998-4
=> A>B(A-B=1998.1998-(1998.1998-4)=4)
b) A=2000.2000
B=1990.2010=(2000-10)(2000+10)=2000.2000-100
=> A>B(A-B=2000.2000-(2000.2000-100)=100)
c) A=25.(31+2)-10=25.31+50-10=25.31+40
B=31.26+10=31(25+1)+10=25.31+31+10=25.31+41
=>B>A(B-A=25.31+41-(25.31+40)=1)
d) A=32.53-31=53(31+1)-31=53.31+53-31=53.31+22
B=53.31+32
=>B>A(B-A=53.31+32-(53.31+22)=10)