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a.-1,75-(-\(\dfrac{1}{9}\)-2\(\dfrac{1}{8}\))
-1,75-\(\dfrac{1}{9}+\dfrac{17}{8}\)
\(-\dfrac{7}{4}-\dfrac{1}{9}+\dfrac{17}{8}\)
\(\dfrac{-126}{72}-\dfrac{8}{72}+\dfrac{153}{72}\)
=\(\dfrac{19}{72}\)
b.\(\dfrac{-1}{12}-\left(2\dfrac{5}{8}-\dfrac{1}{3}\right)\)
\(\dfrac{-1}{12}-\left(\dfrac{21}{8}-\dfrac{1}{3}\right)\)
\(\dfrac{-1}{12}-\dfrac{21}{8}+\dfrac{1}{3}\)
\(\dfrac{-2}{24}-\dfrac{63}{24}+\dfrac{64}{24}\)
=\(\dfrac{-1}{24}\)
Bài 2 :
a,\(\frac{x-1}{3}=2-\frac{x}{-2}\)
\(\Leftrightarrow\frac{x-1}{3}=\frac{-4-x}{-2}\Leftrightarrow-2x+2=-12-3x\Leftrightarrow x=-14\)
b, \(\frac{x-1}{x+5}=\frac{6}{7}\Leftrightarrow7x-7=6x+30\Leftrightarrow x=37\)
c, \(\frac{2x-1}{4}=\frac{4}{2x-1}\Leftrightarrow\left(2x-1\right)^2=16\)
\(\Leftrightarrow\left(2x-1\right)^2-4^2=0\Leftrightarrow\left(2x-5\right)\left(2x+3\right)=0\Leftrightarrow x=\frac{5}{2};-\frac{3}{2}\)
1/
a)19/20
b)(1/4+4/9):(3/2-2/3)^2
=25/36:25/36
=1
2/
a) =>x.4=2.-3
=>x.4=-6
=>x=-1,5
b) =>1/6x=5/3+1/4
=>1/6x=23/12
=>x=11,5
\(a,\left(\frac{3}{8}+-\frac{3}{4}+\frac{7}{12}\right):\frac{5}{6}+\frac{1}{2}\)
= \(\left(-\frac{3}{8}+\frac{7}{12}\right):\frac{5}{6}+\frac{1}{2}\)
= \(\frac{5}{24}:\frac{5}{6}+\frac{1}{2}\)
= \(\frac{1}{4}+\frac{1}{2}\)
= \(\frac{3}{4}\)
b)\(-\frac{7}{3}.\frac{5}{9}+\frac{4}{9}.\left(-\frac{3}{7}\right)+\frac{17}{7}\)
=\(-\frac{35}{27}+\left(-\frac{4}{21}\right)+\frac{17}{7}\)
= \(-\frac{35}{27}+\frac{47}{21}\)
= \(\frac{178}{189}\)
c) \(\frac{117}{13}-\left(\frac{2}{5}+\frac{57}{13}\right)\)
= \(\frac{117}{13}-\frac{311}{65}\)
= \(\frac{274}{65}\)
d) \(\frac{2}{3}-0,25:\frac{3}{4}+\frac{5}{8}.4\)
= \(\frac{2}{3}-\frac{1}{4}:\frac{3}{4}+\frac{5}{8}.4\)
= \(\frac{2}{3}-\frac{1}{3}+\frac{5}{2}\)
= \(\frac{1}{3}+\frac{5}{2}\)
= \(\frac{17}{6}\)
a) 1/4(x-3)+2=1/5
1/4.(x-3) = 1/5-2
1/4.(x-3) = -9/5
x-3 = (-9/5):1/4
x-3 = -36/5
x = -36/5+3
x= -21/5
1.Thực hiện phép tính:
a, \(\frac{1}{3}.(\frac{-4}{5}).\left(\frac{-1}{2}\right)^2:\frac{1}{2}\)
=\(\frac{1}{3}.\frac{-4}{5}.(\frac{-1}{2}).2\)
=\(\frac{1}{3}.\left(\frac{-4}{5}\right).\left(\frac{-1}{2}\right).2\)
=\(\frac{1}{3}.\frac{-4}{5}.\left(-1\right)\)
=\(\frac{1}{3}.\frac{4}{5}=\frac{4}{15}\)
b,\(\left(1+\frac{1}{3}-\frac{2}{5}\right)-\left(2-\frac{2}{3}-\frac{3}{5}\right)+\left(3-\frac{4}{3}-\frac{1}{5}\right)\)
=\(1+\frac{1}{3}-\frac{2}{5}-2+\frac{2}{3}+\frac{3}{5}+3-\frac{4}{3}-\frac{1}{5}\)
=(1+2+3)+\(\left(\frac{1}{3}+\frac{2}{3}-\frac{4}{3}\right)-\left(\frac{2}{5}-\frac{3}{5}+\frac{1}{5}\right)\)
=2+\(\frac{-1}{3}-0\)
=\(\frac{5}{3}-0=\frac{5}{3}\)
2.Tìm x, biết:
a,\(\frac{1}{x}.\frac{-2}{7}=\frac{3}{8}\)
\(\frac{1}{x}=\frac{3}{8}:\frac{-2}{7}\)
\(\frac{1}{x}=\frac{-21}{16}\)\(\Rightarrow x=\frac{-21}{16}\)
b,\(\left|x-\frac{1}{4}\right|=\frac{2}{3}\)
\(\Leftrightarrow\left[{}\begin{matrix}x-\frac{1}{4}=\frac{-2}{3}\\x-\frac{1}{4}=\frac{2}{3}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\frac{-5}{12}\\x=\frac{11}{12}\end{matrix}\right.\)
Vậy:\(x\in\left\{\frac{-5}{12};\frac{11}{12}\right\}\)
3,Tìm a,b\(\in Z\)
a,-19<a<\(\frac{-20}{3}\)
\(\Rightarrow\frac{-57}{3}< \frac{-3a}{3}< \frac{-20}{3}\)
\(\Rightarrow\) -57<-3a<-20
\(\Rightarrow\) a\(\in\)\(\left\{-7;-8;...;-16\right\}\)
b,\(\frac{1}{3}< \frac{4}{b}< \frac{1}{2}\)
Ta có:\(\frac{4}{12}< \frac{4}{b}< \frac{4}{8}\)
\(\Rightarrow12< b< 8\)
Vì quy đồng tử thì mẫu nào lớn hơn thì số đó bé hơn nên:
\(b\in\left\{9;10;11\right\}\)
CHÚC BẠN CÓ MỘT BÀI LÀM THẬT TỐT NHÉ!!!
Bn ơi câu a) bài 3 là -19/2<a<-20/3
Mk ghi sai đề bn làm lại mk vs ạ camơn