1a=169/196
1b-10
1c=20/3
1d=144
1e=-4
1f=-891/100
1g=-21/4
1h=53
1i=151/5
1k=-17
câu b đợi xíu
Bài 3:
\(a,\Rightarrow\dfrac{x}{2}=\dfrac{y}{-5}=\dfrac{x-y}{2+5}=\dfrac{-7}{7}=-1\\ \Rightarrow\left\{{}\begin{matrix}x=-2\\y=5\end{matrix}\right.\\ b,\Rightarrow\dfrac{x}{3}=\dfrac{y}{7}=\dfrac{z-y}{3-7}=\dfrac{16}{-4}=-4\\ \Rightarrow\left\{{}\begin{matrix}x=-12\\y=-28\end{matrix}\right.\\ c,\Rightarrow\dfrac{x}{8}=\dfrac{y}{12}=\dfrac{z}{15}=\dfrac{x+y-z}{8+12-15}=\dfrac{10}{5}=2\\ \Rightarrow\left\{{}\begin{matrix}x=16\\y=24\\z=30\end{matrix}\right.\\ d,\Rightarrow\dfrac{a}{4}=\dfrac{b}{2};\dfrac{b}{5}=\dfrac{c}{3}\Rightarrow\dfrac{a}{20}=\dfrac{b}{10}=\dfrac{c}{6}=\dfrac{a+2b-3c}{20+20-18}=\dfrac{99}{22}=\dfrac{9}{2}\\ \Rightarrow\left\{{}\begin{matrix}a=90\\b=45\\c=27\end{matrix}\right.\)
