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17/21>17/29>15/29 (tự KL) b)(chép đề) B= (20+21)/(21+22)=41/43<1 (chép đề sai). Xét A= 20/21+21/22=1-1/21+1-1/22=1+1-(1/21+1/22). Ta thấy (1/21+1/22)<1 nên 1-(1/21+1/22)>0
a)\(\frac{21}{11}x\frac{22}{17}x\frac{68}{63}\)
=\(\frac{21x22x68}{11x17x63}\)
=\(\frac{21x11x2x17x4}{11x17x21x3}\)
=\(\frac{2x4}{3}\)
=\(\frac{8}{3}\)
b)\(\frac{5}{14}x\frac{7}{13}x\frac{26}{25}\)
=\(\frac{5x7x26}{14x13x25}\)
a) \(\frac{21\times11\times2\times17\times4}{11\times17\times21\times3}=\frac{2\times4}{3}_{ }=\frac{8}{3}\)
b)\(\frac{5\times7\times13\times2}{7\times2\times13\times5\times5}=\frac{1}{5}\)
a)\(\frac{21x22x68}{11x17x63}\) = \(\frac{1x2x4}{1x1x3}\) =\(\frac{8}{3}\)
b)\(\frac{5x7x26}{14x13x25}\) = \(\frac{1x1x2}{2x1x5}\) =\(\frac{1x1x1}{1x1x5}\) = \(\frac{1}{5}\)
ta có: \(1-\frac{17}{20}=\frac{3}{20};1-\frac{22}{25}=\frac{3}{25}\)
\(\Rightarrow\frac{3}{20}>\frac{3}{25}\Rightarrow1-\frac{17}{20}>1-\frac{22}{25}\)
\(\Rightarrow\frac{17}{20}< \frac{22}{25}\)
a) 11x2x17x4x21/11x17x63=8/3
b)5x7x13x2/2x7x13x5x5=1/5
\(\frac{21}{11}\cdot\frac{22}{17}\cdot\frac{68}{63}\)
\(=\frac{1}{1}\cdot\frac{2}{1}\cdot\frac{4}{3}\)
\(=\frac{8}{3}\)
a) (21x11x2x17x4)/(11x17x21x3)
=(21x11x2x17x4)/(11x17x21x3)
=8/3
b) (5x7x13x2)/(7x2x13x5x5)
=1/5
17/21>17/29>15/29 (tự KL)
b)(chép đề)
B= (20+21)/(21+22)=41/43<1 (chép đề sai).
Xét A= 20/21+21/22=1-1/21+1-1/22=1+1-(1/21+1/22).
Ta thấy (1/21+1/22)<1
nên 1-(1/21+1/22)>0
Vậy 1+1-(1/21+1/22)>1+0>1
Vậy A>B