So sánh :
a, \(1,25^2\) và \(\left(1,25\right)^2\);
b, \(\left(2^2\right)^{^3}\) và \(2^{2^3}\).
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\(\left|-1,25:\dfrac{7}{4}\right|+\left|-\dfrac{2}{7}\right|=\left|-\dfrac{5}{4}.\dfrac{4}{7}\right|+\dfrac{2}{7}\)
\(=\dfrac{5}{7}+\dfrac{2}{7}=1\)
\(\left|-1.25:\dfrac{7}{4}\right|+\left|\dfrac{-2}{7}\right|\)
\(=\left|\dfrac{-5}{4}\cdot\dfrac{4}{7}\right|+\left|\dfrac{-2}{7}\right|\)
\(=\dfrac{5}{7}+\dfrac{2}{7}=1\)
\(=\left(\dfrac{1}{2}-\dfrac{6}{5}\right):\dfrac{21}{20}-\dfrac{25}{4}+\dfrac{1}{2}=\dfrac{-7}{10}\cdot\dfrac{20}{21}-\dfrac{23}{4}\)
\(=\dfrac{-2}{3}-\dfrac{23}{4}=\dfrac{-8-69}{12}=-\dfrac{77}{12}\)
\(A=4.\dfrac{25}{16}+25.\left[\dfrac{9}{16}:\dfrac{125}{64}\right]:\dfrac{-27}{8}\)
\(=\dfrac{25}{16}+25.\dfrac{36}{125}:\dfrac{-27}{8}=-\dfrac{137}{240}\left(1\right)\)
\(B=125.\left[\dfrac{1}{25}+\dfrac{1}{64}:8\right]-64.\dfrac{1}{64}\)
\(=125.\dfrac{89}{1600}:8-64.\dfrac{1}{64}=\dfrac{-67}{512}\left(2\right)\)
Vì (2) > (1) => B > A
a) \(...=0,25+1500+\left(0,5\right)^2=0,25+0,25=1500=1500,5\)
b) \(...=2,7-4,4+5,6-7,3=2,7+5,6-4,4-7,3=8,3-11,7=-3,4\)
c) \(...=-5,44+5+0,44=-5,44+0,44+5=-5+5=0\)
d) \(...=6,72+5,27-0,72-1,27=6,72-0,72+5,27-1,27=6+4=10\)
\(2012^0.\left(1,25-\dfrac{1}{4}\right)+\left(\dfrac{3}{5}\right)^8.\left(0,6\right)^7-\left|-5^2\right|\)
\(=1,25-\dfrac{1}{4}+\left(\dfrac{3}{5}\right)^8.\left(0,6\right)^7-\left|-25\right|\)
\(=1,25-\dfrac{1}{4}+\left(\dfrac{3}{5}\right)^8.\left(0,6\right)^7-25\)
\(=1,25-0,25+\left(\dfrac{3}{5}\right)^8.\left(0,6\right)^7-25\)
\(=1+\left(\dfrac{3}{5}\right)^8.\left(0,6\right)^7-25\)
\(=1+\left(\dfrac{3}{5}\right)^8.\left(\dfrac{3}{5}\right)^7-25\)
\(=1+\left(\dfrac{3}{5}\right)^{8+7}-25\)
\(=1+\left(\dfrac{3}{5}\right)^{15}-25\)
\(=1+\dfrac{3^{15}}{5^{15}}-25\)
\(=1,000470185-25\)
\(=-23,99952982\)
\(1,25:\dfrac{15}{20}+\left(25\%-\dfrac{5}{6}\right):4\dfrac{2}{3}\)
\(=\dfrac{5}{4}.\dfrac{4}{3}+\left(\dfrac{1}{4}-\dfrac{5}{6}\right).\dfrac{3}{14}\)
\(=\dfrac{5}{3}+\dfrac{7}{12}.\dfrac{3}{14}\)
\(=\dfrac{5}{3}+-\dfrac{1}{8}\)
\(=\dfrac{37}{24}\)
\(1,25:\dfrac{15}{20}+\left(25\%-\dfrac{5}{6}\right):4\dfrac{2}{3}\)
\(=\dfrac{5}{4}:\dfrac{3}{4}+\left(\dfrac{1}{4}-\dfrac{5}{6}\right):\dfrac{14}{3}\)
\(=\dfrac{5}{4}.\dfrac{4}{3}+\left(\dfrac{-7}{12}\right).\dfrac{3}{14}\)
= \(\dfrac{5}{3}-\dfrac{1}{8}=\dfrac{37}{24}\)
Giải
a, Ta có :
\(25^2=625\text{ }\Rightarrow\text{ }1,25^2=1,625\)
\((1,25)^2=1,25\times1,25=1,5625\)
Vì \(1,625\ne1,5625\Rightarrow1,25^2\ne\left(1,25\right)^2\).
b, Ta có :
\(\left(2^2\right)^{^3}=2^{2\times3}=2^6=64\)
\(2^{2^3}=2^8=256\)
Vì \(64\ne256\Rightarrow\left(2^2\right)^{^3}\ne2^{2^3}\).
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a ) \(1,25^2=1,5625\)
\(\left(1,25\right)^2=1,5625\)
= > 1,25 2 = ( 1,25 )2
b) \(\left(2^2\right)^3=64\)
\(2^{2^3}=256\)
= > \(2^{2^3}>\left(2^2\right)^3\)