`@Khói`
Câu `20` : `=>C`
Vì `M` nằm giữa `E` và `F` ko có nghĩa là `M` là trung điểm của `EF`
Câu `1` :
`a)60%-`\(4\dfrac{1}{2}+\dfrac{2}{3}\)
`=3/5-9/2+2/3`
`=18/30-135/30+20/30`
`=-97/30`
câu 20C
bài 1
a)\(=\dfrac{3}{5}-\dfrac{9}{2}+\dfrac{2}{3}=\dfrac{18}{30}-\dfrac{135}{30}+\dfrac{20}{30}=-\dfrac{97}{30}\)
b)\(=\left(\dfrac{31}{17}-\dfrac{14}{17}\right)+\left(-\dfrac{5}{13}-\dfrac{8}{13}\right)=1+\left(-1\right)=0\)
c)\(=\dfrac{5}{11}\cdot\dfrac{-9}{13}+\dfrac{5}{11}\cdot\dfrac{-4}{13}+\dfrac{16}{11}\)
\(=\dfrac{5}{11}\left(\dfrac{-9}{13}-\dfrac{4}{13}\right)=-\dfrac{5}{11}+\dfrac{16}{11}=\dfrac{9}{11}\)
`b)31/17+ -5/13+ -8/13-14/17`
`=(31/17-14/17)+(-5/13+ -8/13)`
`=1+ -13/13`
`=1+(-1)`
`=0`
