cho A=1/11+1/12+1/13+1/14+...+1/50
so sánh A với 1/2
cho B=1/50+1/51+1/52+...+1/98+1/99
chứng minh rằng b <1/2
cho C=1/10+1/11+1/12+...+1/99+1/100
chứng tỏ C >1
CM: 11/10 bé hơn 1/11+1/12+1/13+...+1/49+1/50 bé hơn 5/2
a)Cho A= 3/10+3/11+3/12+3/13+3/14.
Chứng minh A<3/2
b)Cho B=1/11+1/12+1/13+....+1/20.
Chứng minh 7/12<B<5/6c
c)Cho C=1/5+1/6+....+1/17
Chứng minh C>1
1/11 + 1/12 + 1/13 + ... + 1/49 + 1/50 > 16/15
1/11 + 1/12 + 1/13 + ... + 1/49 + 1/50 > 8/3
tính :
C= 1/11 + 1/12 + 1/13 +...+ 1/49 + 1/50
S=1/10+1/11+1/12+1/13+1/14+.....+1/49.so sánh S với 1/50
bài 1:
a) 10\17+5\-13-11\25+7\17-8\13
b) 0,3-93\7-70%0-4\7
c)1\8+1\24+1\48+...+1\2400
d) 3\41-12\17+33\49
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12\41-48\17+132\49
a)11/53+(32/47+-10/53)+-64/94+1/53+1/3
b) (-1+45/115+47/51)+(-9/23+-1/3)
c) -13/49+12/48+1/12+3/18
d) 13/15+(-4/5+7/18)+-5/12+1/16
1. Thực hiện phép tính ( tính nhanh )
a, -6/35 : -54/49
b,-5/7.2/11+5/7.9/11+1 1/5
c,( 1/3 + 3/4 - 13/12 ) : ( 12/13 +123/234 +1234/2345 )