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A=\(\frac{1}{2}.\frac{2}{3}.\frac{3}{4}...\frac{2014}{2015}.\frac{2015}{2016}\)
A=\(\frac{1.2.3.4...2015}{2.3.4...2016}=\frac{1}{2016}\)
Hok tốt
A = \(\left(1-\frac{1}{2}\right).\left(1-\frac{1}{3}\right).\left(1-\frac{1}{4}\right)...\left(1-\frac{1}{2015}\right).\left(1-\frac{1}{2016}\right)\)
= \(\frac{1}{2}.\frac{2}{3}.\frac{3}{4}...\frac{2014}{2015}.\frac{2015}{2016}\)
= \(\frac{1}{2016}\)
Vậy ...
\(\Rightarrow\)\(\frac{2}{6}\)+ \(\frac{2}{12}\)+ \(\frac{2}{20}\)+...+\(\frac{2}{x\left(x+1\right)}\)= \(\frac{2011}{2013}\)
\(\Rightarrow\)\(\frac{2}{2.3}\)+ \(\frac{2}{3.4}\)+ \(\frac{2}{4.5}\)+...+ \(\frac{2}{x\left(x+1\right)}\)= \(\frac{2011}{2013}\)
\(\Rightarrow\)\(\frac{1}{2}\)- \(\frac{1}{3}\)+ \(\frac{1}{3}\)- \(\frac{1}{4}\)+...+ \(\frac{1}{x}\)- \(\frac{1}{x+1}\)= \(\frac{2011}{2013}\): 2
\(\Rightarrow\)\(\frac{1}{2}\)- \(\frac{1}{x+1}\)= \(\frac{2011}{4026}\)
\(\Rightarrow\)\(\frac{1}{x+1}\)= \(\frac{1}{2}\)- \(\frac{2011}{4026}\)= \(\frac{1}{2013}\)
\(\Rightarrow\)\(x+1=2013\)
Tìm x, biết
\(2.3^x=3^{12}.10+8.12^{12}\)
NHANH GIÚP MÌNH NHA, MÌNH ĐANG CẦN GẤP
NẾU ĐÚNG MÌNH TICK CHO
a, [(-23)+(-125)]+(37+221)+(-79)
=(-148)+258+(-79)
=110+(-79)=31
b, (-123)+34+(-65)+(-77)+125
=[(-123)+(-77)]+[(-65)+125]+34
=(-200)+60+34
=(-140)+34=106
có j sai mong bạn thông cảm
a, (-23)+37+(-79)+(-125)+221
=[-23+(-79)+(-125)]+(37+221)
=-227+258
=485
b, (-123)+34+(-65)+(-77)+125
=[-123+(-77)]+(-65+125)+34
=-200+60+34
=-140+34
=-106
c, (-48)+79+(-33)+(-76)+241
=[-48+(-33)+(-76)]+(79+241)
=-157+320
=163
A,153.177-153.77+100.(-77)
=153.(177-77)+100.(-77)
=153.100+100.(-77)
=100.(153+(-77))
=100.76
=7600
a)153.177-153.77+100+100.(-77)
=153.(177-77)+100.[1+(-77)]
=153.100+100.(-76)
=100.[153+(-76)]
=100.77=7700
b)(-29).(85-47)-85.(47-29)
=(-29).85+29.47-85.47+85.29
=85.[(-29)+29]+47.(29-85)
=85.0+47.(-56)
=0+(-2632)
c)(-167) . (67-34) - 67 . ( 34- 167)
=-167.67+167.34 - 67.34+67.167
=167.34-67.34
=34.(167-67)
=34.100=3400
a) \(12.53+53.172-53.84=53.\left(12+172-84\right)=53.100=5300\)
b) \(33.77+66.77+77=77.\left(33+66+1\right)=77.100=7700\)
c) \(79.35+79.77+21.83+21.29=79.\left(35+77\right)+21.\left(83+29\right)\)
\(=79.112+21.112=112\left(79+21\right)=112.100=11200\)
53.(12+172-84)
=53.100=5300 tương tự còn lại tự làm