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A = 1 - \(\dfrac{5}{6}\)+\(\dfrac{7}{12}\)-\(\dfrac{9}{20}\)+\(\dfrac{11}{30}\)-\(\dfrac{13}{42}\)+\(\dfrac{15}{56}\) - \(\dfrac{17}{72}\)+\(\dfrac{19}{90}\)+\(\dfrac{23}{132}\)-\(\dfrac{25}{156}\)
A = 1 - \(\dfrac{5}{2.3}\)+\(\dfrac{7}{3.4}\)-\(\dfrac{9}{4.5}\)+\(\dfrac{11}{5.6}\)-\(\dfrac{13}{6.7}\)+\(\dfrac{15}{7.8}\)-\(\dfrac{17}{8.9}\)+\(\dfrac{19}{9.10}\)+\(\dfrac{23}{11.12}\)-\(\dfrac{25}{12.13}\)
A = 1 - \(\dfrac{1}{2}-\dfrac{1}{3}\)+\(\dfrac{1}{3}+\dfrac{1}{4}\)-\(\dfrac{1}{4}-\dfrac{1}{5}\)+...+\(\dfrac{1}{11}+\dfrac{1}{12}\)- \(\dfrac{1}{12}-\dfrac{1}{13}\)
A = 1 - \(\dfrac{1}{2}\) - \(\dfrac{1}{13}\)
A = \(\dfrac{1}{2}\) - \(\dfrac{1}{13}\)
A = \(\dfrac{11}{26}\)
1+2+3+4+5+6+7+8+9+10=55
11+12+13+14+15+16+17+18+19+20=155
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+30-50-53=362
ta có
1/2<1/1.2
1/3<1/2.3
...
1/32<1/31.32
=>1/2+1/3+...+1/32<1/1.2+1/2.3+...+1/31.32
=>1/2+1/3+...+1/32<1/1-1/2+1/2-1/3+...+1/31-1/32
=>1/2+1/3+...+1/32<1/1-1/32=31/32
vì 31/32<1
=>tổng đó <1
ta lại có 1+1=2 mà 2 <3
=>tổng đó <3
vậy:-------(bn tự lm nha)
k cho mik vs nha
bn tham khảo câu trả lời của mik ở bn hoàng thu trang nhabây h mik ghi lại dài dòng lắm
1
a) \(\frac{14}{7}+\frac{5}{9}+\frac{4}{9}-2\)
\(=2\frac{5}{9}+\frac{4}{9}-2\)
\(=3-2=1\)
b) \(\frac{31}{25}+\left(\frac{15}{16}-\frac{6}{15}\right)+\frac{1}{16}\)
\(=\frac{31}{25}+\frac{43}{80}+\frac{1}{16}\)
\(=1\frac{311}{400}+\frac{1}{16}\)
\(=1\frac{21}{25}\)