Cho C= \(\frac{1}{20}\)+ \(\frac{1}{21}\)+ \(\frac{1}{22}\)+ ... + \(\frac{1}{200}\)
CMR C > \(\frac{9}{10}\)
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CHO
S=\(\frac{1}{20}+\frac{1}{21}+\frac{1}{22}+...+\frac{1}{199}+\frac{1}{200}\)
CHỨNG MINH RẰNG S>\(\frac{9}{10}\)
S = \(\frac{1}{20}+\frac{1}{21}...+\frac{1}{199}+\frac{1}{200}\) ( có 181 phân số )
=> S > \(\frac{1}{200}+\frac{1}{200}+...+\frac{1}{200}+\frac{1}{200}\)
=> S > \(\frac{1}{200}.181\)
=> S > \(\frac{181}{200}\)> \(\frac{180}{200}\)= \(\frac{9}{10}\)
Vậy S > 9 / 10
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GIÚP NHA , AI LÀM ĐƯƠC 1 NGÀY TK 3TK
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S = \(\frac{1}{20}\)+ \(\frac{1}{21}\)+ ....+\(\frac{1}{200}\)có 181 p/s
mà \(\frac{1}{20}\)>\(\frac{1}{200}\)
.............
\(\frac{1}{199}\)>\(\frac{1}{200}\)
\(\frac{1}{200}\)=\(\frac{1}{200}\)
nên ta có S > \(\frac{1}{200}\)+ \(\frac{1}{200}\)+..... có 181 phân số \(\frac{1}{200}\)
vậy \(\frac{1}{200}\)*181=\(\frac{181}{200}\)mà \(\frac{181}{200}\)>\(\frac{9}{10}\)mà \(\frac{1}{20}\)+......+\(\frac{1}{200}\)(có 181 số)>\(\frac{1}{200}\)+\(\frac{1}{200}\)(có 181 p/s \(\frac{1}{200}\))>\(\frac{9}{10}\)
Vậy ==> S>\(\frac{9}{10}\)
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1)
\(Cho:\frac{1}{20}+\frac{1}{21}+\frac{1}{22}+...+\frac{1}{200}\)
Chứng minh: \(A>\frac{9}{10}\)
2)
Cho \(B=\frac{1}{101}+\frac{1}{102}+\frac{1}{103}+...+\frac{1}{200}\)
Chứng minh \(B>\frac{7}{12}\)
1)
Cho \(\frac{1}{20}+\frac{1}{21}+\frac{1}{22}+...+\frac{1}{200}\)
Chứng minh: \(A>\frac{9}{10}\)
2)
Cho \(B=\frac{1}{101}+\frac{1}{102}+\frac{1}{103}+...+\frac{1}{200}\)
Chứng minh: \(B>\frac{7}{12}\)
1 . Tinh : a , left(1-frac{1}{6}right)left(1-frac{1}{10}right)left(1-frac{1}{14}right).....left(1-frac{1}{5050}right)b,frac{^{2^{19}}.left(3^3right)^3+3.5.left(2^2right)^9.left(3^2right)^4}{left(2.3right)^9.2^{10}+left(3.2^2right)^{10}}c,frac{18.frac{19}{2}.frac{20}{3}.frac{21}{4}.....frac{36}{19}}{20.frac{21}{2}.frac{22}{3}.....frac{36}{17}}giup mjk nha mjk tjk cho
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1 . Tinh : a , \(\left(1-\frac{1}{6}\right)\left(1-\frac{1}{10}\right)\left(1-\frac{1}{14}\right).....\left(1-\frac{1}{5050}\right)\)b,\(\frac{^{2^{19}}.\left(3^3\right)^3+3.5.\left(2^2\right)^9.\left(3^2\right)^4}{\left(2.3\right)^9.2^{10}+\left(3.2^2\right)^{10}}\)c,\(\frac{18.\frac{19}{2}.\frac{20}{3}.\frac{21}{4}.....\frac{36}{19}}{20.\frac{21}{2}.\frac{22}{3}.....\frac{36}{17}}\)giup mjk nha mjk tjk cho
Giải các pt sau:
a. -\(\frac{5}{9}\)x +1=\(\frac{2}{3}\)x - 10
b. \(\frac{x-22}{8}+\frac{x-21}{9}+\frac{x-20}{10}+\frac{x-19}{11}=4\)
c. ( 5x +3)(x2 + 4 )(x - 4) = 0
d. ( 2x - 1)2 + ( 2 - x )( 2x - 1) = 0
https://i.imgur.com/hUeQcNa.jpg
\(\frac{-5}{9}x+1=\frac{2}{3}x-10\)
\(\frac{-5}{9}x+\frac{9}{9}=\frac{6}{9}x-\frac{90}{9}\)
\(-5x+9=6x-90\)
\(-5x-6x=-90-9\)
\(-11x=-99\)
\(x=\frac{-99}{-11}=9\)
b. \(\frac{x-22}{8}+\frac{x-21}{9}+\frac{x-20}{10}+\frac{x-19}{11}=4\)
\(\frac{x-22}{8}-1+\frac{x-21}{9}-1+\frac{x-20}{10}-1+\frac{x-19}{11}-1=0\)
\(\frac{x-30}{8}+\frac{x-30}{9}+\frac{x-30}{10}+\frac{x-30}{11}=0\)
\(\left(x-30\right)\left(\frac{1}{8}+\frac{1}{9}+\frac{1}{10}+\frac{1}{11}\right)=0\)
x=30
Chúc bạn học tốt!!
C/m ::
\(S=\frac{1}{12}+\frac{1}{13}+\frac{1}{14}+\frac{1}{15}+\frac{1}{16}+\frac{1}{17}+\frac{1}{18}+\frac{1}{19}+\frac{1}{20}+\frac{1}{21}+\frac{1}{22}>\frac{1}{2}\)
Giải phương trình:
a)\(\frac{x+81}{19}+\frac{x+82}{18}=\frac{x+84}{16}+\frac{x+85}{15}\)
b)\(\frac{x-22}{8}+\frac{x-21}{9}+\frac{x-20}{10}+\frac{x-19}{11}=4\)
c)\(\frac{x+19}{3}+\frac{x+13}{5}=\frac{x+7}{7}+\frac{x+1}{9}\)
d)\(\frac{2-x}{2018}-1=\frac{1-x}{2019}-\frac{x}{2020}\)
https://i.imgur.com/s9QrL5D.jpg
https://i.imgur.com/7p0hoi8.jpg
a,\(\frac{1995\cdot1994-1}{1994+1996\cdot1995}\)b,\(\frac{864\cdot48-432\cdot96}{864\cdot48\cdot432}\)c,\(\frac{1414+1515+1616+1717+1818+1919}{20\cdot20+21\cdot21+22\cdot22+23\cdot23+24\cdot24+25\cdot25}\)
d,\(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+\frac{1}{15}+\frac{1}{21}+...+\frac{1}{3240}\)
Đây là những bài lớp 5+ vậy nên không làm theo kiểu lớp 5 được, cố gắng tìm bài đúng lớp nhé bạn (VNNLL cc)
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1.CMR:
a) Cho a, b, c là các số nguyên dương
\(1<\frac{a}{b+c}+\frac{b}{c+a}+\frac{c}{a+b}<2\)
b) \(S3=\frac{1}{5}+\frac{1}{13}+\frac{1}{25}+...+\frac{1}{10^2+11^2}<\frac{9}{20}\)