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Bài 1:
a)
\(A=\dfrac{-5}{6}\cdot\dfrac{3}{10}\\ =\dfrac{\left(-5\right)\cdot3}{6\cdot10}\\ =\dfrac{-1}{4}\)
b)
\(B=\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{12}\\ =\dfrac{4}{12}-\dfrac{3}{12}+\dfrac{1}{12}\\ =\dfrac{4-3+1}{12}\\ =\dfrac{1}{6}\)
Bài 2:
\(A=\left(\dfrac{-1}{5}\right)\cdot\dfrac{15}{4}+\left|\dfrac{4}{5}-\dfrac{14}{5}\right|:\dfrac{8}{3}\\ =\left(\dfrac{-1}{5}\right)\cdot\dfrac{15}{4}+\left|\dfrac{-10}{5}\right|\cdot\dfrac{3}{8}\\ =\left(\dfrac{-1}{5}\right)\cdot\dfrac{15}{4}+2\cdot\dfrac{3}{8}\\ =\dfrac{-3}{4}+\dfrac{3}{4}\\ =0\)
\(B=\left(\dfrac{-1}{2}\right)^2:1\dfrac{3}{8}+25\%\cdot\dfrac{3}{11}\\ =\left(\dfrac{-1}{2}\right)^2:\dfrac{11}{8}+\dfrac{3}{4}\cdot\dfrac{3}{11}\\ =\dfrac{1}{4}\cdot\dfrac{8}{11}+\dfrac{3}{4}\cdot\dfrac{3}{11}\\ =\dfrac{8}{44}+\dfrac{9}{44}\\ =\dfrac{17}{44}\)
\(C=\dfrac{-8}{5}+0,6+\left|\dfrac{-1}{2}\right|+\dfrac{1}{2}\\ =\dfrac{-8}{5}+\dfrac{3}{5}+\dfrac{1}{2}+\dfrac{1}{2}\\ =\left(\dfrac{-8}{5}+\dfrac{3}{8}\right)+\left(\dfrac{1}{2}+\dfrac{1}{2}\right)\\ =\left(-1\right)+1\\ =0\)
\(D=\dfrac{-5}{9}\cdot\dfrac{2}{13}+\dfrac{-5}{9}:\dfrac{13}{11}+1\dfrac{5}{9}\\ =\dfrac{-5}{9}\cdot\dfrac{2}{13}+\dfrac{-5}{9}\cdot\dfrac{11}{13}+\dfrac{14}{9}\\ =\dfrac{-5}{9}\cdot\left(\dfrac{2}{13}+\dfrac{11}{13}\right)+\dfrac{14}{9}\\ =\dfrac{-5}{9}\cdot1+\dfrac{14}{9}\\ =\dfrac{-5}{9}+\dfrac{14}{9}\\ =1\)
Bài 1:
1: =-5/24+16/27+3/4
=-5/24+18/24+16/27
=13/24+16/27
=117/216+128/216=245/216
2: =-1/3+1/3+6/7=6/7
3: \(=\dfrac{1}{2}-\dfrac{7}{12}+\dfrac{1}{2}=1-\dfrac{7}{12}=\dfrac{5}{12}\)
4: \(=-\dfrac{5}{8}+\dfrac{14}{25}-\dfrac{6}{10}=\dfrac{-125+112-120}{200}=\dfrac{-133}{200}\)
1.
a, => 21-x+3 < 0
=> 24-x < 0
=> x < 24
b, => 7+x > 0
=> x > -7
c, => x-1 < 0 ; x+2 > 0 ( vì x-1 < x+2 )
=> x < 1 ; x > -2
=> -2 < x < 1
Tk mk nha
Bài 1: Dễ, tính máy tính là ra
Bài 2:
a) \(\dfrac{1}{5}+1\dfrac{1}{4}x=\dfrac{2}{3}\)
\(\Rightarrow1\dfrac{1}{4}x=\dfrac{7}{15}\Rightarrow x=\dfrac{28}{75}\)
Vậy \(x=\dfrac{28}{75}\)
b) \(\left(\dfrac{2}{7}x-1\dfrac{1}{2}x\right):\dfrac{2}{7}=\dfrac{-21}{4}\)
\(\Rightarrow\left(\dfrac{2}{7}x-\dfrac{3}{2}x\right):\dfrac{2}{7}=\dfrac{-21}{4}\)
\(\Rightarrow\dfrac{2}{7}x-\dfrac{3}{2}x=\dfrac{-3}{2}\)
\(\Rightarrow x\left(\dfrac{2}{7}-\dfrac{3}{2}\right)=\dfrac{-3}{2}\)
\(\Rightarrow\dfrac{-17}{14}x=\dfrac{-3}{2}\Rightarrow x=\dfrac{21}{17}\)
Vậy \(x=\dfrac{21}{17}\)
c) \(\dfrac{5}{8}+\dfrac{1}{3}:x=\dfrac{1}{2}\)
\(\Rightarrow\dfrac{1}{3}:x=\dfrac{-1}{8}\Rightarrow x=\dfrac{-8}{3}\)
Vậy \(x=\dfrac{-8}{3}\)
d) \(\dfrac{-5}{6}+\dfrac{8}{3}+\dfrac{-29}{6}< x< \dfrac{-1}{2}+2+\dfrac{5}{2}\)
\(\Rightarrow-3< x< 4\)
\(\Rightarrow x\in\left\{-2;-1;0;1;2;3\right\}\) vì x thuộc Z
Vậy \(\Rightarrow x\in\left\{-2;-1;0;1;2;3\right\}\)
Các bạn ơi giúp mk trả lời mấy câu hỏi này với mk đang cần rất gấp ngay bây giờ đây nè!!!!!