Tính:
\(A=1+\frac{1}{2}\times\left(1+2\right)+\frac{1}{3}\times\left(1+2+3\right)+...+\frac{1}{16}\times\left(1+2+3+...+16\right)\)
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Tính nhanh\(A=1+\frac{1}{2}\times\left(1+2\right)+\frac{1}{3}\times\left(1+2+3\right)+\frac{1}{4}\times\left(1+2+3+4\right)+...+\frac{1}{16}\times\left(1+2+...+16\right)\)
\(A=1+\frac{1}{2}.\left(1+2\right)+\frac{1}{3}.\left(1+2+3\right)+...+\frac{1}{16}.\left(1+2+...+16\right)\)
\(=1+\frac{1}{2}.2.3:2+\frac{1}{3}.3.4:2+...+\frac{1}{16}.16.17:2=1+\frac{3}{2}+\frac{4}{2}+...+\frac{17}{2}=\frac{2+3+4+...+17}{2}=\frac{152}{2}=76\)
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tính các tích sauafrac{3}{4}timesfrac{8}{9}timesfrac{15}{16}times...timesfrac{9999}{10000}bleft(1-frac{1}{4}right)timesleft(1-frac{1}{9}right)times...timesleft(1-frac{1}{10000}right)cleft(1-frac{1}{2}right)timesleft(1-frac{1}{3}right)times...timesleft(1-frac{1}{1994}right)dleft(1+frac{1}{1times3}right)timesleft(1+frac{1}{2times4}right)timesleft(1+frac{1}{3times5}right)times...timesleft(1+frac{1}{99times100}right)
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tính các tích sau
\(a=\frac{3}{4}\times\frac{8}{9}\times\frac{15}{16}\times...\times\frac{9999}{10000}\)
\(b=\left(1-\frac{1}{4}\right)\times\left(1-\frac{1}{9}\right)\times...\times\left(1-\frac{1}{10000}\right)\)
\(c=\left(1-\frac{1}{2}\right)\times\left(1-\frac{1}{3}\right)\times...\times\left(1-\frac{1}{1994}\right)\)
\(d=\left(1+\frac{1}{1\times3}\right)\times\left(1+\frac{1}{2\times4}\right)\times\left(1+\frac{1}{3\times5}\right)\times...\times\left(1+\frac{1}{99\times100}\right)\)
\(d=\left(1+\frac{1}{1.3}\right)\left(1+\frac{1}{2.4}\right)\left(1+\frac{1}{3.5}\right).........\left(1+\frac{1}{99.101}\right)\)
\(=\frac{4}{3}.\frac{9}{2.4}.............\frac{10000}{99.101}\)
\(=\frac{2.2}{3}.\frac{3.3}{2.4}.\frac{4.4}{3.5}............\frac{100.100}{99.101}\)
\(=\frac{2.3.4..........100}{2.3.4............99}.\frac{2.3.4...........100}{3.4...........101}\)
\(=100.\frac{2}{101}\)\(=\frac{200}{101}\)
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\(C=\left(1-\frac{1}{2}\right)\times\left(1-\frac{1}{3}\right)\times...\times\left(1-\frac{1}{1994}\right)\)
\(=\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times...\times\frac{1993}{1994}\)
\(=\frac{1\times2\times3\times...\times1993}{2\times3\times4\times...\times1994}\)
\(=\frac{1}{1994}\) (Giản ước còn lại như này)
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tính giá trị biểu thứca, Afrac{-1}{2}-left[frac{-3}{5}right]+left[frac{-1}{9}right]+frac{1}{27}+frac{7}{18}+frac{4}{35}-left[-frac{2}{7}right]b, Bfrac{1}{3}-frac{3}{4}-left[frac{-3}{5}-frac{1}{57}+frac{1}{36}+frac{-1}{15}right]-frac{2}{9}c, Cleft[-frac{7}{15}right]timesfrac{5}{8}timesleft[frac{30}{-7}right]timesleft[-16right]timesleft[frac{-1}{1000}right]d, Dfrac{1}{2}timesfrac{-11}{19}-50%timesleft[-frac{1}{19}right]+frac{10}{19}timesfrac{1111}{2222}
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tính giá trị biểu thức
a, A=\(\frac{-1}{2}-\left[\frac{-3}{5}\right]+\left[\frac{-1}{9}\right]+\frac{1}{27}+\frac{7}{18}+\frac{4}{35}-\left[-\frac{2}{7}\right]\)
b, B=\(\frac{1}{3}-\frac{3}{4}-\left[\frac{-3}{5}-\frac{1}{57}+\frac{1}{36}+\frac{-1}{15}\right]-\frac{2}{9}\)
c, C=\(\left[-\frac{7}{15}\right]\times\frac{5}{8}\times\left[\frac{30}{-7}\right]\times\left[-16\right]\times\left[\frac{-1}{1000}\right]\)
d, D=\(\frac{1}{2}\times\frac{-11}{19}-50\%\times\left[-\frac{1}{19}\right]+\frac{10}{19}\times\frac{1111}{2222}\)
tính giá trị biểu thức chứ còn cái gì nữa
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a, \(A=\frac{22}{27}\)
b,\(B=\frac{1}{57}\)
C,\(C=\frac{1}{50}\)
d, \(D=0\)
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1.Tính nhanha,frac{1}{1times4}+frac{1}{4times7}+............+frac{1}{97times100}b,frac{1}{2}timesfrac{2}{3}timesfrac{3}{4}times...........timesfrac{99}{100}c,frac{3}{4}timesfrac{8}{9}timesfrac{15}{16}times...........timesfrac{99}{100}d,left(frac{1}{2}+1right)timesleft(frac{1}{3}+1right)timesleft(frac{1}{4}+1right)times............timesleft(frac{1}{99}+1right)e,left(1-frac{1}{2}right)timesleft(1-frac{1}{3}right)timesleft(1-frac{1}{4}right)times..........timesleft(1-frac{1}{100}right)
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1.Tính nhanh
a,\(\frac{1}{1\times4}+\frac{1}{4\times7}+............+\frac{1}{97\times100}\)
b,\(\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times...........\times\frac{99}{100}\)
c,\(\frac{3}{4}\times\frac{8}{9}\times\frac{15}{16}\times...........\times\frac{99}{100}\)
d,\(\left(\frac{1}{2}+1\right)\times\left(\frac{1}{3}+1\right)\times\left(\frac{1}{4}+1\right)\times............\times\left(\frac{1}{99}+1\right)\)
e,\(\left(1-\frac{1}{2}\right)\times\left(1-\frac{1}{3}\right)\times\left(1-\frac{1}{4}\right)\times..........\times\left(1-\frac{1}{100}\right)\)
a,Đặt \(A=\frac{1}{1\times4}+\frac{1}{4\times7}+...+\frac{1}{97\times100}\)
\(\Rightarrow3A=\frac{3}{1\times4}+\frac{3}{4\times7}+...+\frac{3}{97\times100}\)
\(\Rightarrow3A=\frac{1}{1}-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+...+\frac{1}{97}-\frac{1}{100}\)
\(\Rightarrow3A=1-\frac{1}{100}=\frac{99}{100}\)
\(\Rightarrow A=\frac{99}{300}\)
b, \(\frac{1}{2}\times\frac{2}{3}\times...\times\frac{99}{100}=\frac{1\times2\times...\times99}{2\times3\times...\times1000}=\frac{1}{100}\)
c, \(\frac{3}{4}\times\frac{8}{9}\times...\times\frac{99}{100}=\frac{1.3}{2.2}\times\frac{2.4}{3.3}\times...\times\frac{9.11}{10.10}=\frac{1.2.....9}{2.3.....10}\times\frac{3.4.....11}{2.3.....10}=\frac{1}{10}\times\frac{11}{2}=\frac{11}{20}\) (dấu . là dấu nhân)
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BÀI 1:TÍNHAfrac{7^2}{7times8}timesfrac{8^2}{8times9}times...timesfrac{11^2}{11times12}Bleft(1+frac{1}{11}right)timesleft(1+frac{1}{12}right)times...timesleft(1+frac{1}{15}right)Cleft(1-frac{1}{2}right)timesleft(1-frac{1}{3}right)timesleft(1-frac{1}{4}right)times...timesleft(1-frac{1}{2010}right)Dleft(frac{1}{2}-1right)timesleft(frac{1}{3}-1right)timesleft(frac{1}{4}-1right)times...timesleft(frac{1}{2010}-1right)BÀI 2: Tìm phân số tối giản frac{a}{b}nhỏ nhất (a,b thuộc N sao)để khi nhân frac{a}{b...
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BÀI 1:TÍNH
A=\(\frac{7^2}{7\times8}\times\frac{8^2}{8\times9}\times...\times\frac{11^2}{11\times12}\)
B=\(\left(1+\frac{1}{11}\right)\times\left(1+\frac{1}{12}\right)\times...\times\left(1+\frac{1}{15}\right)\)
C=\(\left(1-\frac{1}{2}\right)\times\left(1-\frac{1}{3}\right)\times\left(1-\frac{1}{4}\right)\times...\times\left(1-\frac{1}{2010}\right)\)
D=\(\left(\frac{1}{2}-1\right)\times\left(\frac{1}{3}-1\right)\times\left(\frac{1}{4}-1\right)\times...\times\left(\frac{1}{2010}-1\right)\)
BÀI 2: Tìm phân số tối giản \(\frac{a}{b}\)nhỏ nhất (a,b thuộc N sao)để khi nhân \(\frac{a}{b}với\frac{55}{16}:\frac{25}{24}\)được tích là các số tự nhiên.
\(B=\frac{12}{11}x\frac{13}{12}x.......x\frac{16}{15}\)
\(=\frac{16}{11}\)
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Tìm tích:
1.\(\left(\frac{1}{2}+1\right)\times\left(\frac{1}{3}+1\right)\times\left(\frac{1}{4}+1\right)\times...\times\left(\frac{1}{999}+1\right)\)
2.\(\left(\frac{1}{2}-1\right)\times\left(\frac{1}{3}-1\right)\times\left(\frac{1}{4}-1\right)\times...\times\left(\frac{1}{1000}-1\right)\)
3.\(\frac{3}{2^2}\times\frac{8}{3^2}\times\frac{15}{4^2}\times...\times\frac{99}{10^2}\)
biết làm bài 1 thôi
\(\left(\frac{1}{2}+1\right)\times\left(\frac{1}{3}+1\right)\times\cdot\cdot\cdot\times\left(\frac{1}{999}+1\right)\)
= \(\frac{3}{2}\times\frac{4}{3}\times\frac{5}{4}\times\cdot\cdot\cdot\times\frac{1000}{999}\)
lượt bỏ đi còn :
\(\frac{1000}{2}=500\)
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Tính giá trị biểu thức: A=\(\frac{\left(1+17\right)\times\left(1+\frac{17}{2}\right)\times\left(1+\frac{17}{3}\right)....\left(1+\frac{17}{19}\right)}{\left(1+19\right)\times\left(1+\frac{19}{2}\right)\times\left(1+\frac{19}{3}\right)....\left(1+\frac{19}{17}\right)}\)
BÀI 1:TÍNHAfrac{7^2}{7times8}timesfrac{8^2}{8times9}times...timesfrac{11^2}{11times12}Bleft(1+frac{1}{11}right)timesleft(1+frac{1}{12}right)times...1+frac{1}{15}Cleft(1-frac{1}{2}right)timesleft(1-frac{1}{3}right)timesleft(1-frac{1}{4}right)times...timesleft(1-frac{1}{2010}right)Dleft(frac{1}{2}-1right)timesleft(frac{1}{3}-1right)timesleft(frac{1}{4}-1right)times...timesleft(frac{1}{2010}-1right)BÀI 2:Tìm p/số tối giản frac{a}{b}nhỏ nhất (a,bin Ncdotđể khi nhân frac{a}{b}vớifrac{55}{16};frac{25}...
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BÀI 1:TÍNH
A=\(\frac{7^2}{7\times8}\times\frac{8^2}{8\times9}\times...\times\frac{11^2}{11\times12}\)
B=\(\left(1+\frac{1}{11}\right)\times\left(1+\frac{1}{12}\right)\times...1+\frac{1}{15}\)
C=\(\left(1-\frac{1}{2}\right)\times\left(1-\frac{1}{3}\right)\times\left(1-\frac{1}{4}\right)\times...\times\left(1-\frac{1}{2010}\right)\)
D=\(\left(\frac{1}{2}-1\right)\times\left(\frac{1}{3}-1\right)\times\left(\frac{1}{4}-1\right)\times...\times\left(\frac{1}{2010}-1\right)\)
BÀI 2:Tìm p/số tối giản \(\frac{a}{b}\)nhỏ nhất (a,b\(\in N\cdot\)để khi nhân \(\frac{a}{b}với\frac{55}{16};\frac{25}{24}\)thì ta được tích là các số tự nhiên
Tính giá trị biểu thức:
\(A=\frac{\frac{16}{10}:\left(1\frac{3}{5}\times \frac{5}{4}\right)}{\frac{64}{100}-\frac{1}{25}}+\frac{\left(\frac{108}{100}-\frac{2}{25}\right):\frac{4}{7}}{\left(5\frac{5}{9}-2\frac{1}{4}\right)\times 2\frac{2}{17}}+\frac{3}{5}\times \frac{1}{2}:\frac{2}{5}\)