a ) A = 1 7 − 1 13 = 6 91 .
b ) B = 1 3 − 1 27 = 8 27 c ) C = 1 4 4 3.7 + 4 7.11 + 4 11.15 + 4 15.19 + 4 19.23 + 4 23.27 = 2 27 d ) D = 1 5 1 − 1 31 = 6 31
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Tính hợp lí: a) A dfrac{1}{56} + dfrac{1}{72} + dfrac{1}{90} + dfrac{1}{110} + dfrac{1}{132} + dfrac{1}{156} ; b) B dfrac{4}{21} + dfrac{4}{77} + dfrac{4}{165} + dfrac{4}{285} +dfrac{4}{437} +dfrac{4}{621}; c) C dfrac{1}{21} + dfrac{1}{77} +dfrac{1}{165} +dfrac{1}{285} +dfrac{1}{437} +dfrac{1}{621} ; d) D dfrac{1}{1.6} + dfrac{1}{6.11} +dfrac{1}{11.16} +dfrac{1}{16.21} +dfrac{1}{26.31} .
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Tính hợp lí:
a) A = \(\dfrac{1}{56}\) + \(\dfrac{1}{72}\) + \(\dfrac{1}{90}\) + \(\dfrac{1}{110}\) + \(\dfrac{1}{132}\) + \(\dfrac{1}{156}\) ;
b) B = \(\dfrac{4}{21}\) + \(\dfrac{4}{77}\) + \(\dfrac{4}{165}\) + \(\dfrac{4}{285}\) +\(\dfrac{4}{437}\) +\(\dfrac{4}{621}\);
c) C = \(\dfrac{1}{21}\) + \(\dfrac{1}{77}\) +\(\dfrac{1}{165}\) +\(\dfrac{1}{285}\) +\(\dfrac{1}{437}\) +\(\dfrac{1}{621}\) ;
d) D = \(\dfrac{1}{1.6}\) + \(\dfrac{1}{6.11}\) +\(\dfrac{1}{11.16}\) +\(\dfrac{1}{16.21}\) +\(\dfrac{1}{26.31}\) .
\(D=\frac{4}{21}+\frac{4}{77}+\frac{4}{165}+\frac{4}{285}+\frac{4}{437}+\frac{4}{621}\)
Tính A biết :\(A=\frac{1}{21}+\frac{1}{77}+\frac{1}{165}+\frac{1}{285}+\frac{1}{437}\)
tính giá trị biểu thứcAfrac{-378.132+189.64}{15+18+21+......+45+48}B1,4.frac{15}{14}-left(frac{4}{5}+frac{2}{5}right):2frac{1}{5}-frac{frac{73}{77}+frac{73}{165}+frac{73}{285}}{frac{25}{24}+frac{15}{180}+frac{20}{285}}Cfrac{7+frac{7}{12}-frac{7}{144}+frac{7}{60}}{5+frac{6}{12}-frac{5}{144}}.frac{frac{3}{4}-frac{3}{16}+frac{3}{64}-frac{3}{256}}{1-frac{1}{4}+frac{1}{16}-frac{1}{34}}-frac{1}{20}
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tính giá trị biểu thức
\(A=\frac{-378.132+189.64}{15+18+21+......+45+48}\)
\(B=1,4.\frac{15}{14}-\left(\frac{4}{5}+\frac{2}{5}\right):2\frac{1}{5}-\frac{\frac{73}{77}+\frac{73}{165}+\frac{73}{285}}{\frac{25}{24}+\frac{15}{180}+\frac{20}{285}}\)
\(C=\frac{7+\frac{7}{12}-\frac{7}{144}+\frac{7}{60}}{5+\frac{6}{12}-\frac{5}{144}}.\frac{\frac{3}{4}-\frac{3}{16}+\frac{3}{64}-\frac{3}{256}}{1-\frac{1}{4}+\frac{1}{16}-\frac{1}{34}}-\frac{1}{20}\)
Bài 1:Thực hiện phép tính sau:
(4/77+4/165+4/285):(5/84+3/180+4/285)
Bài 2:Tìm x:
(x+2/3).-3/5+4/7-11/7x
\(0,25:\left(10,3-9,8\right)-\frac{3}{4}\\ b,\left(3\frac{4}{5}-2.x\right).1\frac{1}{3}\\ c,\frac{x}{7}=\frac{6}{-21}\\ d,\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}+\frac{1}{110}+\frac{ }{132}\)cái cuối là 1/132
Tính giá trị biểu thức
\(A=\frac{-378.132+189.64}{15+18+21+...+45+48}\)
\(B=1,4.\frac{15}{14}-\left(\frac{4}{5}+\frac{2}{5}\right):2\frac{1}{5}-\frac{\frac{73}{77}+\frac{73}{165}+\frac{73}{285}}{\frac{25}{24}+\frac{15}{180}+\frac{20}{285}}\)
Tính nhanh:
A=10 - 1/72 - 1/50 - 1/42- .... - 1/6 - 1/2
Tìm x:
a.(x+1) + (x+1/3) +(x+1/6) +...+(x+1/55)= 130/11
b. 2/3.x - 780/11 :(13/15 +13/3535+13/63+1313/9999) +5=0
c. 2012/77 +20112/165 +2012/258 +2012/437=16/161 .x
Cảm ơn nhiều!!!!!!!!!!!
Bài 1:Thực hiện phép tínha,frac{left(2^3.5.7right)left(5^2.7^3right)}{(2.5.7^2)^2}b,frac{4}{77}+frac{4}{165}+frac{4}{285}:frac{5}{84}+frac{3}{180}+frac{4}{285}Bài 2:Tìm x,ya,left(x+frac{2}{3}right).frac{-3}{5}+frac{4}{7}1frac{4}{7}.xb,|5x-2|le0c,(x-7).(x+3) 0d,(x-3).(2y+1)7(vớix,ynguyên)
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Bài 1:Thực hiện phép tính
\(a,\frac{\left(2^3.5.7\right)\left(5^2.7^3\right)}{(2.5.7^2)^2}\)
\(b,\frac{4}{77}+\frac{4}{165}+\frac{4}{285}:\frac{5}{84}+\frac{3}{180}+\frac{4}{285}\)
Bài 2:Tìm x,y
\(a,\left(x+\frac{2}{3}\right).\frac{-3}{5}+\frac{4}{7}=1\frac{4}{7}.x\)
\(b,|5x-2|\le0\)
\(c,(x-7).(x+3)< 0\)
\(d,(x-3).(2y+1)=7\)\((với\)\(x,y\)nguyên)
| a) 3/13 + 7/12 - 10/13 + 5/12 | d) -5/10 + 12/28 - 3/27 - 7/18 + 20/35 |
| b) 15/24 - 6/26 + 28/48 - 30/39 + 10/24 | e) 1/56 + 1/72 + 1/90 + 1/110 + 1/132+ 1/156 = |
| c) -1/2 + 3/7 - 1/9 - 7/18 + 4/7 = |