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26 tháng 6 2022
a: \(=\dfrac{-4}{7}+\dfrac{7}{16}=\dfrac{-64+49}{112}=\dfrac{-15}{112}\)
b: \(=\dfrac{5}{16}\cdot32=10\)
c: \(=\dfrac{\left(-3\right)^2}{5^2}=\dfrac{9}{25}\)
d: \(=\dfrac{4}{5}\cdot\dfrac{-3+2}{10}=\dfrac{4}{5}\cdot\dfrac{-1}{10}=\dfrac{-4}{50}=\dfrac{-2}{25}\)
NR
20 tháng 7 2017
(x + \(\dfrac{1}{2}\) ) + (x + \(\dfrac{1}{8}\) ) + (x+\(\dfrac{1}{8}\))+(x+\(\dfrac{1}{16}\))=1
4x + \(\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}\)=1
4x +\(\dfrac{15}{16}\)=1
4x = 1 -\(\dfrac{15}{16}\)
4x=\(\dfrac{1}{16}\)
x=\(\dfrac{1}{16}\div4\)
x=\(\dfrac{1}{64}\)
16 tháng 6 2022
a: \(\dfrac{-5}{6}=\dfrac{-20}{24};\dfrac{7}{8}=\dfrac{21}{24};\dfrac{7}{24}=\dfrac{7}{24};\dfrac{-3}{4}=-\dfrac{18}{24};\dfrac{2}{3}=\dfrac{16}{24}\)
Do đó: \(\dfrac{-5}{6}< -\dfrac{3}{4}< \dfrac{7}{24}< \dfrac{2}{3}< \dfrac{7}{8}\)
\(\dfrac{7}{8}=\dfrac{119}{136};\dfrac{16}{17}=\dfrac{128}{136}\)
mà 119<128
nên 7/8<16/17
DO đó: -5/6<-3/4<7/24<2/3<7/8<16/17
b: \(\dfrac{-5}{8}=\dfrac{-95}{8\cdot19};\dfrac{-16}{19}=\dfrac{-128}{19\cdot8}\)
Do đó: -5/8>-16/19
\(\dfrac{7}{10}=0.7;\dfrac{20}{23}\simeq0.87;\dfrac{214}{315}\simeq0.68;\dfrac{205}{107}>1\)
Do đó: \(\dfrac{205}{107}>\dfrac{20}{23}>\dfrac{7}{10}>\dfrac{214}{315}>-\dfrac{5}{8}>-\dfrac{16}{19}\)
19 tháng 3 2017
\(\dfrac{3}{4}.\dfrac{8}{9}.\dfrac{15}{16}....\dfrac{624}{625}\)
\(=\dfrac{3.8.15...624}{4.9.16...625}\)
\(=\dfrac{\left(1.3\right)\left(2.4\right)\left(3.5\right)...\left(24.26\right)}{\left(2.2\right)\left(3.3\right)\left(4.4\right)...\left(25.25\right)}\)
\(=\dfrac{\left(1.2.3...24\right)\left(3.4.5...26\right)}{\left(2.3.4...25\right).\left(2.3.4...25\right)}\)
\(=\dfrac{1.26}{25.2}\)
\(=\dfrac{13}{25}\)
BN
19 tháng 3 2017
\(\dfrac{3}{4}\cdot\dfrac{8}{9}\cdot\dfrac{15}{16}\cdot\cdot\cdot\dfrac{624}{625}\)
\(=\dfrac{1.3}{2.2}\cdot\dfrac{2.4}{3.3}\cdot\dfrac{3.5}{4.4}\cdot\cdot\cdot\dfrac{24.26}{25.25}\)
\(=\dfrac{1.2.3....24}{2.3.4....25}\cdot\dfrac{3.4.5....26}{2.3.4...25}\)
\(=\dfrac{1}{25}\cdot\dfrac{26}{2}=\dfrac{13}{25}\)
29 tháng 12 2017
a/ \(\dfrac{-5}{x}\) = \(\dfrac{-18}{72}\)
\(\Rightarrow\dfrac{5}{x}=\dfrac{18}{72}=\dfrac{1}{4}\)
\(\Rightarrow x=5:\dfrac{1}{4}=20\)
\(\dfrac{y}{16}=\dfrac{-18}{72}\) \(=\dfrac{-1}{4}\)
\(\Leftrightarrow\) 4y = - 16
\(\Leftrightarrow\) y = -4
Vậy x = 20 ; y = -4
b/ \(\dfrac{1}{2}=\dfrac{x-1}{8}=\dfrac{10}{y-5}\)
\(\Rightarrow\dfrac{x-1}{8}=\dfrac{1}{2}\)
\(\Rightarrow\dfrac{x-1}{8}=\dfrac{4}{8}\)
\(\Rightarrow x-1=4\)
\(\Rightarrow\) \(x=4+1\)
\(x=5\)
\(\dfrac{10}{y-5}=\dfrac{1}{2}\)
\(\Rightarrow\dfrac{10}{y-5}=\dfrac{10}{20}\)
\(\Rightarrow\) \(y-5=20\)
\(\Rightarrow y=20+5\)
\(y=25\)
Vậy x = 5 ; y = 25
NT
29 tháng 12 2017
a)
\(-\dfrac{5}{x}=-\dfrac{18}{72}\\ \Leftrightarrow\dfrac{5}{x}=\dfrac{18}{72}=\dfrac{1}{4}\\ \Leftrightarrow x=20\)
\(\dfrac{y}{16}=\dfrac{-18}{72}=-\dfrac{1}{4}\\ \Leftrightarrow4y=-16\\ \Leftrightarrow y=-4\)
b)
\(\dfrac{x-1}{8}=\dfrac{1}{2}\Rightarrow\dfrac{x-1}{8}=\dfrac{4}{8}\Rightarrow x-1=4\Rightarrow x=5\)
\(\dfrac{10}{y-5}=\dfrac{1}{2}\Leftrightarrow y-5=20\Leftrightarrow y=25\)
11 tháng 4 2017
\(\dfrac{48}{25}\cdot\dfrac{27}{55}+2\dfrac{4}{9}\cdot\dfrac{14}{33}\)
\(=\dfrac{1296}{1375}+\dfrac{22}{9}\cdot\dfrac{14}{33}\\ =\dfrac{1296}{1375}+\dfrac{28}{27}\\ =\dfrac{34992}{37125}+\dfrac{38500}{37125}\\ =\dfrac{73492}{37125}\)
\(1\dfrac{19}{22}\cdot\left(\dfrac{47}{77}-\dfrac{16}{15}\right)\\ =\dfrac{41}{22}\cdot\dfrac{-527}{1155}\\ =\dfrac{-21607}{25410}\)
\(\left(3\dfrac{10}{99}+4\dfrac{11}{99}-5\dfrac{8}{299}\right)-\left(\dfrac{1}{2}-\dfrac{1}{3}-\dfrac{1}{6}\right)\\ =\left(\dfrac{307}{99}+\dfrac{37}{99}-\dfrac{1503}{299}\right)-0\\ =\dfrac{344}{99}-\dfrac{1053}{299}\\ =-\dfrac{107}{2277}\)
\(x\cdot\dfrac{8}{16}=\dfrac{32}{16}\)
\(\Leftrightarrow x=\dfrac{32}{16}:\dfrac{8}{16}\)
\(\Leftrightarrow x=\dfrac{32}{16}\cdot\dfrac{16}{8}\)
\(\Leftrightarrow x=4\)
X=32/16:8/16
=>x=4