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13 D
14 A
15 A
16 C
17 B
18 A
19 C
20 B
1 the cleverest
2 longer
3 the best
4 cleaner
5 more expensive
6 the most quickly
7 more dangerous
8 more sweetly
9 the most exciting
10 the fastest
1 beautifully
2 carefully
3 badly
4 quietly
5 loud
6 happily
7 fast
8 well
9 terribly
10 early
11 hard
12 late
Bài 2:
a: 3/8=81/216
5/27=40/216
b: -2/9=-50/225
4/25=36/225
c: 1/15=1/15
-6=-90/15
\(\Leftrightarrow\left\{{}\begin{matrix}2x-3y=3\sqrt{5}-1\\4x+\left(2\sqrt{5}+2\right)y=-4\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}4x-6y=6\sqrt{5}-2\\4x+\left(2\sqrt{5}+2\right)y=-4\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}\left(-8-2\sqrt{5}\right)y=6\sqrt{5}+2\\2x-3y=3\sqrt{5}-1\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=1-\sqrt{5}\\x=\dfrac{3\sqrt{2}-3\sqrt{5}+2}{2}\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}4x-6y=6\sqrt{5}-2\\3.\left(\sqrt{5}-1\right)x+6y=3-3\sqrt{5}\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}\left(3\sqrt{5}+1\right)x=1+3\sqrt{5}\\y=\dfrac{3\sqrt{5}-1-2x}{-3}\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x=1\\y=\dfrac{3\sqrt{5}-1-2.1}{-3}\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x=1\\y=\dfrac{-3.\left(1-\sqrt{5}\right)}{-3}=1-\sqrt{5}\end{matrix}\right.\\ \Rightarrow\left(x;y\right)=\left(1;1-\sqrt{5}\right)\)
36 D
37 B
38 C
39 C
40 D
41 D
42 A
43 D
44 D
45 A
46 D
47 B
48 C
49 D
50 D
51 B
52 C
53 B
54 C
55 C
56 C
57 B
58 A
59 C
60 B
61 B
62 C
63 C
64 C
cảm ơn bạn