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\(A=\left(-\dfrac{2}{5}+\dfrac{10}{3}\right):\left(-\dfrac{2}{5}+\dfrac{10}{3}\right)=1\\ e,\Rightarrow\left[{}\begin{matrix}5x-1=0\\2x=\dfrac{1}{3}\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\dfrac{1}{5}\\x=\dfrac{1}{6}\end{matrix}\right.\)
2 câu kia đề mờ quá b
\(=0,5\cdot27-\dfrac{1}{9}:\left(-\dfrac{1}{27}\right)=\dfrac{1}{2}\cdot27+\dfrac{1}{9}\cdot27=27\left(\dfrac{1}{2}+\dfrac{1}{9}\right)=27\cdot\dfrac{11}{18}=\dfrac{33}{2}\)
12D
Bài 1:
\(a,=\left(\dfrac{11}{19}+\dfrac{8}{19}\right)+\left(\dfrac{19}{18}-\dfrac{1}{18}\right)+5,2=1+1+5,2=7,2\\ c,=\left(\dfrac{5}{12}:\dfrac{10}{3}\right)+\left(\dfrac{1}{6}\right)^2=\dfrac{1}{8}+\dfrac{1}{36}=\dfrac{11}{72}\\ d,=\dfrac{2^4\cdot2^3}{2^6}=2\)
Bài 2:
\(a,\Rightarrow\dfrac{2}{3}x=\dfrac{3}{10}\Rightarrow x=\dfrac{9}{20}\\ b,\Rightarrow x=\dfrac{-2\cdot27}{3,6}=-15\\ c,\Rightarrow\left|x-12\right|=2017\\ \Rightarrow\left[{}\begin{matrix}x-12=2017\\12-x=2017\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=2029\\x=-2005\end{matrix}\right.\)
a: góc ABM=góc AEF
góc AMB=góc AFE
mà góc AEF=góc AFE
nên góc ABM=góc AMB
=>ΔABM cân tại A
b: Kẻ BN//FC
Xét ΔBDN và ΔCDF có
góc DBN=góc DCF
DB=DC
góc BDN=góc CDF
=>BN=FC
góc BNE=góc AFE
=>góc BNE=góc BEN
=>BN=BE=FC=MF
\(2,\\ a,\Leftrightarrow\dfrac{3}{7}x=\dfrac{9}{14}\Leftrightarrow x=\dfrac{3}{2}\\ b,\Leftrightarrow9,18x=-10,83\\ \Leftrightarrow x=-\dfrac{361}{306}\\ 3,\\ a,=4-2+0,6=2,6\\ b,=\dfrac{3+39}{7+91}=\dfrac{42}{98}=\dfrac{3}{7}\)
b: Xét tứ giác ABDC có
I là trung điểm của AD
I là trung điểm của BC
Do đó: ABDC là hình bình hành
Suy ra: CD//AB và CD=AB
a) ĐKXĐ: \(x\ge0\)
\(\Leftrightarrow\dfrac{1}{2}\sqrt{x}+\dfrac{9}{4}=\dfrac{5}{2}\\ \Leftrightarrow\dfrac{1}{2}\sqrt{x}=\dfrac{1}{4}\\ \Leftrightarrow\sqrt{x}=\dfrac{1}{2}\\ \Leftrightarrow x=\dfrac{1}{4}\)
b) \(\dfrac{x}{2}=\dfrac{y}{3}\Rightarrow\dfrac{x}{10}=\dfrac{y}{15}\)
\(\dfrac{y}{5}=\dfrac{z}{4}\Rightarrow\dfrac{y}{15}=\dfrac{z}{12}\)
\(\Rightarrow\dfrac{x}{10}=\dfrac{y}{15}=\dfrac{z}{12}\)
Áp dụng t/c dtsbn ta có:
\(\dfrac{x}{10}=\dfrac{y}{15}=\dfrac{z}{12}=\dfrac{x-y+z}{10-15+12}=-\dfrac{49}{7}=-7\)
\(\dfrac{x}{10}=-7\Rightarrow x=-70\\ \dfrac{y}{15}=-7\Rightarrow y=-105\\ \dfrac{z}{12}=-7\Rightarrow z=-84\)
\(\dfrac{1}{2}\sqrt{x}+\sqrt{\dfrac{81}{16}=\dfrac{5}{2}}\)
\(\dfrac{1}{2}\sqrt{x}+\dfrac{9}{4}=\dfrac{5}{2}\)
\(\dfrac{1}{2}\sqrt{x}=\dfrac{5}{2}-\dfrac{9}{4}\)
\(\dfrac{1}{2}\sqrt{x}=\dfrac{1}{4}\)
\(\sqrt{x=}\dfrac{1}{4}:\dfrac{1}{2}\)
\(\sqrt{x}=\dfrac{1}{2}\)
x=\(\dfrac{1}{4}\)