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a) \(\frac{2005\cdot2006-1}{2006\cdot2004+2005}\)
\(=\frac{2004\cdot2006+2006-1}{2006\cdot2004+2005}\)
\(=1\)
b) \(27\left(\frac{171717}{272727}+\frac{373737}{363636}\right)\)
\(=27\left(\frac{17}{27}+\frac{37}{36}\right)\)
\(=27\cdot\frac{17}{27}+27\cdot\frac{37}{36}\)
\(=17+\frac{9\cdot3\cdot37}{9\cdot4}\)
\(=17+27,75=44,75\)
P/s : ko biết câu b có đúng ko nữa
37/42+37/56+37/72 = 37(1/42+1/56+1/72)=37( 1/6.7 + 1/7.8 + 1/8.9 )= 37( 1/6 - 1/7 + 1/7 - 1/8 + 1/8 - 1/9)= 37( 1/6 - 1/9)= 37.1/18=37/18
\(\frac{27}{31}=\frac{2727}{3131}=\frac{272727}{313131}\)
\(\frac{27}{31}=\frac{27.101}{31.101}=\frac{27.10101}{31.10101}\)
\(\frac{27}{31}=\frac{27}{31}=\frac{27}{31}\)
\(\Rightarrow\frac{27}{31}=\frac{2727}{3131}=\frac{272727}{313131}\)
\(\frac{27}{31}=\frac{2727}{3131}=\frac{272727}{313131}\)
\(\frac{27}{31}=\frac{27\cdot101}{31\cdot101}=\frac{27\cdot10101}{31\cdot10101}\)
\(\Rightarrow\frac{27}{31}=\frac{2727}{3131}=\frac{272727}{313131}\)
\(\frac{5454}{5757}-\frac{171717}{191919}=\frac{18.303}{19.303}-\frac{17.10101}{19.10101}=\frac{18}{19}-\frac{17}{19}=\frac{1}{19}\)
Ta có :
\(\frac{5454}{5757}=\frac{54.101}{57.101}=\frac{54}{57}\); \(\frac{171717}{191919}=\frac{17.10101}{19.10101}=\frac{17}{19}\)
Vậy \(\frac{54}{57}-\frac{17}{19}=\frac{1}{19}\)
\(\frac{121212+12121212-1212}{363636+36363636-3636}\)
\(=\frac{12.10101+12.1010101-12.101}{36.10101+36.1010101-36.101}\)
\(=\frac{12\left(10101+1010101-101\right)}{36\left(10101+1010101-101\right)}\)
\(=\frac{12}{12.3}\)
\(=\frac{1}{3}\)
Ta có: \(\frac{121212+12121212-1212}{363636+36363636-3636}\)
=\(\frac{12\times\left(10101+1010101-101\right)}{36\times\left(10101+1010101-101\right)}\)
=\(\frac{12}{36}\)
=\(\frac{1}{3}\)
a) \(15\times\left(\frac{212121}{434343}+\frac{333333}{353535}\right)=15\times\left(\frac{21\times10101}{43\times10101}+\frac{33\times10101}{35\times10101}\right)\)
\(=15\times\left(\frac{21}{43}+\frac{33}{35}\right)=\frac{6462}{301}\)
b) \(\frac{639\times721721}{721\times639639}=\frac{639\times721\times1001}{721\times639\times1001}=1\)
c) \(\frac{327\times412+400}{328\times412-12}=\frac{\left(328-1\right)\times412+400}{328\times412-12}=\frac{328\times412-412+400}{328\times412-12}\)
\(=\frac{328\times412-12}{328\times412-12}=1\)
d) \(9\times\left(\frac{151515}{171717}+\frac{131313}{181818}\right)=9\times\left(\frac{15\times10101}{17\times10101}+\frac{13\times10101}{18\times10101}\right)=9\times\left(\frac{15}{17}+\frac{13}{18}\right)\)
\(=9\times\frac{491}{306}=\frac{491}{34}\)
27 x \(\left(\frac{171717}{272727}+\frac{373737}{363636}\right)\)
= 27 x \(\left(\frac{17}{27}+\frac{37}{36}\right)\)
= 27 x \(\frac{17}{27}\)+ 27 x \(\frac{37}{36}\)
= 17 + 27,75
= 44,75
\(\frac{178}{4}\)bạn nhé