Bài 1:
a) 27x58-31=(26+1)x58-31=26x58+58-31=26x58+27
=> E=F
b)G = 1.2.3 + 1.2.2.2.3.2 + 4.1.4.2.4.3 = 1.2.3.( 1 + 2.2.2 + 4.4.4 )
H = 1.3.5 +1.2.2.2.3.2 + 4.1.4.2.4.3 = 1.3.5. ( 1+ 2.2.2 +4.4.4 )
Vì 1.2.3 < 1.3.5 nên G < H
c) I= 2005x2005=2005x(1995+10)=2005x1995+20050
K=1995x(2005+10)=1995x2005+19950
vì 19950<20050 nên 1995x2005+19950<1995x2005+20050 hay K<>
Bài 2:
Ta có: SBC : SC= 3 dư 3
=> SBC=3.SC+3
Mà: SBC+SC+ số dư=50
=> 3.SC+3+SC+3=50
=>4.SC+6=50 =>SC=11
=>SBC=11.3+3=36