Ta thấy :

\(\frac{20}{39}>\frac{14}{39}\)

\(\frac{22}{27}>\frac{22}{29}\)

\(\frac{18}{43}< \frac{18}{41}\)

\(\Rightarrow\frac{20}{39}+\frac{22}{27}+\frac{18}{43}>\frac{14}{39}+\frac{22}{29}+\frac{18}{41}\)

=> A > B

xét A và B,ta thấy:

20/39>14/39

22/27>22/29

18/43<18/41

Ta có: 20/39+22/27>14/39+22/29

2012^2013+2013^2013<2013^2013+2013^2014

xet A va B ta thay:

20/39>14/39

22/27>22/29

18/43<18/41

vay A>B

Ta có: \(\dfrac{20}{39}>\dfrac{20}{41}>\dfrac{18}{41}\left(1\right)\)

\(\dfrac{22}{27}>\dfrac{22}{29}\left(2\right)\)

\(\dfrac{18}{43}=1-\dfrac{25}{43};\dfrac{14}{39}=1-\dfrac{25}{39}\)

Vì \(\dfrac{25}{43}< \dfrac{25}{39}\Rightarrow1-\dfrac{25}{43}>1-\dfrac{25}{39}\Rightarrow\dfrac{18}{43}>\dfrac{14}{39}\left(3\right)\)

Từ \(\left(1\right);\left(2\right);\left(3\right)\) ta suy ra : A>B

300

300

= 300 

áp dụng kiến thức tính nhanh ý

1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30+31+32+33+34+35+36+37+38+39+40+41+42+43+44+45+46+47+48+49+50=1275

= 1275

=1275

=1245

Có ai rảnh đâu mà đi ngồi cộng ngần đấy số ra.