Cho P=\(\frac{20}{30}+\frac{20}{70}+\frac{20}{120}+....+\frac{20}{798}\)
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Tính giá trị biểu thức sau :
\(\frac{20}{30}+\frac{20}{70}+\frac{20}{126}+...+\frac{20}{798}\)
1, tim x bết:,frac{left(-5^4right).left(-15^2right)-5^4.left(-3^2.5right)}{left(-3^4right).25^2-left(-15^2right).225.5}:frac{x}{5}frac{-1}{6}2, cho Afrac{20}{30}+frac{20}{70}+frac{20}{126}+...+frac{20}{798}Bleft(frac{41}{2}.frac{42}{2}.frac{43}{2}...frac{80}{2}right):left(1.3.5...79right)So sánh A và B.3, Tính nhanh.frac{0,875+frac{1}{2}-7%-frac{1}{58}}{frac{1}{25}-frac{1}{2}-frac{2}{7}+frac{2}{203}}-125%HELP ME PLEASE......
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1, tim x bết:
,\(\frac{\left(-5^4\right).\left(-15^2\right)-5^4.\left(-3^2.5\right)}{\left(-3^4\right).25^2-\left(-15^2\right).225.5}\)\(:\)\(\frac{x}{5}\)\(=\frac{-1}{6}\)
2, cho A=\(\frac{20}{30}+\frac{20}{70}+\frac{20}{126}+...+\frac{20}{798}\)
B=\(\left(\frac{41}{2}.\frac{42}{2}.\frac{43}{2}...\frac{80}{2}\right):\left(1.3.5...79\right)\)
So sánh A và B.
3, Tính nhanh.
\(\frac{0,875+\frac{1}{2}-7\%-\frac{1}{58}}{\frac{1}{25}-\frac{1}{2}-\frac{2}{7}+\frac{2}{203}}\)\(-125\%\)
HELP ME PLEASE......
Tính nhanh giá trị biểu thức sau:\(\frac{4}{20}+\frac{9}{30}+\frac{16}{40}+\frac{25}{50}+\frac{36}{60}+\frac{49}{70}+\frac{64}{80}+\frac{81}{90}+\frac{100}{100}+\frac{121}{110}+\frac{144}{120}+\frac{169}{130}\)
=2/10+3/10+4/10+......+13/10
=\(\frac{2+3+4+......+13}{10}\)
=90/10=9
k cho mình nha
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\(\frac{10-x}{100}+\frac{20-x}{110}+\frac{30-x}{120}=3\)
Ta có : \(\frac{10-x}{100}+\frac{20-x}{110}+\frac{30-x}{120}=3\)
<=> \(\frac{10-x}{100}+\frac{20-x}{110}+\frac{30-x}{120}-3=0\)
<=> \(\left(\frac{10-x}{100}-1\right)+\left(\frac{20-x}{110}-1\right)+\left(\frac{30-x}{120}-1\right)\)= 0
<=> \(\left(\frac{-90-x}{100}\right)+\left(\frac{-90-x}{110}\right)+\left(\frac{-90-x}{120}\right)=0\)
<=> (-90-x) \(\left(\frac{1}{100}+\frac{1}{110}+\frac{1}{120}\right)=0\)
<=> -90- x = 0 vì \(\left(\frac{1}{100}+\frac{1}{110}+\frac{1}{120}\right)\ne0\) ( > 0)
<=> -x = 90
<=> x = -90
Vậy x = -90
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(10-x)/100+(20-x)/110+(30-x)/120=3
=>(10-x)/100+(20-x)/110+(30-x)/120-3=0
=>(10-x)/100-1+(20-x)/110-1+(30-x)/120-1=0
=>(-90-x)/100+(-90-x)/110+(-90-x)/120=0
=.>(-90-x)(1/100+1/110+1/120)=0
=.>(-90-x)=0(vì(1/100+1/110+1/120)luôn>0)
=>x=-90
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A=\(\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}+\frac{1}{10.11}+\frac{1}{11.12}+\frac{1}{12.13}+\frac{1}{13.14}\)
B=\(\frac{1}{20}+\frac{-1}{30}+\frac{1}{40}+\frac{-1}{50}+\frac{1}{60}+\frac{-1}{70}+\frac{1}{80}+\frac{1}{70}+\frac{-1}{60}+\frac{1}{50}+\frac{-1}{40}+\frac{1}{30}+\frac{-1}{20}\)
giúp mình giải các bài toán này nha mình đang càn gấp cảm ơn các bạn nhiều
A=\(\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+...+\frac{1}{13}-\frac{1}{14}\)=\(\frac{1}{7}-\frac{1}{14}\)=\(\frac{1}{14}\)
B=0
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\(\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}+\frac{1}{10.11}+\frac{1}{11.12}+\frac{1}{12.13}+\frac{1}{13.14}\)
\(=\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}+\frac{1}{10}-\frac{1}{11}+\frac{1}{11}-\frac{1}{12}+\frac{1}{12}-\frac{1}{13}+\frac{1}{13}-\frac{1}{14}\)
\(=\frac{1}{7}-\frac{1}{14}=\frac{1}{14}\)
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A=\(\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}+\frac{1}{10.11}+\frac{1}{11.12}+\frac{1}{12.13}+\frac{1}{13.14}\)
A=\(\left(\frac{1}{7}-\frac{1}{8}\right).\left(\frac{1}{8}-\frac{1}{9}\right).\left(\frac{1}{9}-\frac{1}{10}\right).\left(\frac{1}{10}-\frac{1}{11}\right).\left(\frac{1}{11}-\frac{1}{12}\right).\left(\frac{1}{12}-\frac{1}{13}\right).\left(\frac{1}{13}-\frac{1}{14}\right)\)
A=\(\frac{1}{7}-\frac{1}{14}\)
A=\(\frac{1}{14}\)
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Tìm x biết: \(\frac{x+10}{90}+\frac{x+20}{80}+\frac{x+30}{70}+\frac{x+40}{60}+\frac{x+50}{50}\)
Tìm x biết: \(\frac{x+10}{90}+\frac{x+20}{80}+\frac{x+30}{70}+\frac{x+40}{60}+\frac{x+50}{50}=-5\)
\(\frac{x+10}{90}+\frac{x+20}{80}+\frac{x+30}{70}+\frac{x+40}{60}+\frac{x+50}{50}=-5\)
<=> \(\frac{x+10}{90}+1+\frac{x+20}{80}+1+\frac{x+30}{70}+1+\frac{x+40}{60}+1+\frac{x+50}{50}+1=0\)
<=> \(\frac{x+100}{90}+\frac{x+100}{80}+\frac{x+100}{70}+\frac{x+100}{60}+\frac{x+100}{50}=0\)
<=> \(\left(x+100\right)\left(\frac{1}{90}+\frac{1}{80}+\frac{1}{70}+\frac{1}{60}+\frac{1}{50}\right)=0\)
<=> x + 100 = 0
<=> x = -100
Vậy x = -100
Tính giá trị biểu thức
\(\frac{1}{10}+\frac{2}{20}+\frac{9}{30}+\frac{16}{40}+\frac{25}{50}+\frac{36}{60}+\frac{49}{70}+\frac{69}{80}+\frac{81}{90}\)
=1/10+1/10+3/10+4/10+5/10+6/10+7/10+8/10+9/10
=1/10+45/10
=46/10=23/5
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Tính bằng cách thuận tiện nhất:
\(\frac{1}{10}+\frac{2}{20}+\frac{3}{30}+\frac{4}{40}+\frac{5}{50}+\frac{6}{60}+\frac{7}{70}+\frac{8}{80}+\frac{9}{90}\)
\(=\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+...+\frac{1}{10}\)có 9 p/số
\(=\frac{1}{10}.9=\frac{9}{10}\)
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= 1/10 + 1/10 + ...................... + 1/10 có 9 phân số
= 1/10 x 9
= 9/10
ai tk mình mình đang bị âm điểm
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9 / 12 bn nha
tk mk nha các bn
thanks nhiêu
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