Giúp e b7 với ạ:) e camon
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Ex6
1 was
2 had been
3 found
4 had talked
5 had spoken
6 snowed
7 were
8 painted
9 had
10 had known
Ex7
2 had got
3 had hurt
4 were
5 were
6 was
7 wanted
8 ?
9 stopped
10 had eaten
9. is/ tells
10. are
11. has
12. isn't
--------
B3
1. is
2. teaches
3. learn
4. comes
5. has
6. goes
7. meets
8. drinks
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B4
1. plays
2. drink
3. starts
4. live
5. do
6. speak
7. watches
------------
B5
1. does -> do
2. Do -> Does
3. watch -> watches
4. goes -> go
5. carries -> carry
6. don't -> doesn't
7. plays -> play
8. are -> is
Bài 5:
\(5^{n+2}+26.5^n+8^{2n+1}\)
\(=25.5^n+26.5^n+8.64^n\)
\(=51.5^n+8.64^n\)
\(=51.5^n+8.5^n+8.64^n-8.5^n\)
\(=59.5^n+8\left(64^n-5^n\right)\)
Ta thấy: \(\left\{{}\begin{matrix}59.5^n⋮59\\8\left(64^n-5^n\right)⋮\left(64-5\right)=59\end{matrix}\right.\)
⇒ \(59.5^n+8\left(64^n-5^n\right)⋮59\)
⇒ \(5^{n+2}+26.5^n+8^{2n+1}\) ⋮ \(59\)
⇒ \(ĐPCM\)
Vì tam giác ABH vuông tại H
\(\Rightarrow AH^2+x^2=AB^2\)
mà AH = 4,8 cm; AB = 6 cm
\(\Rightarrow4,8^2+x^2=6^2\) \(\Rightarrow23,04+x^2=36\) \(\Rightarrow x^2=36-23,04=12,96\) \(\Rightarrow x=3,6\left(cm\right)\)
Vì tam giác ACH vuông tại H
\(\Rightarrow AH^2+y^2=AC^2\)
mà AH = 4,8 cm; AC = 8 cm
\(\Rightarrow4,8^2+y^2=8^2\) \(\Rightarrow23,04+y^2=64\) \(\Rightarrow y^2=64-23,04=40,96\) \(\Rightarrow y=6,4\left(cm\right)\)
Vậy x = 3,6 cm; y = 6,4 cm
~~ Chúc bạn học tốt ~~
áp dụng định lí Py-ta-go vào \(\Delta\) vuông AHC, ta có:
\(AC^2=AH^2+HC^2\)
\(\Rightarrow\)\(HC^2=AC^2-AH^2\)
\(HC^2=8^2-4,8^2\)
\(HC^2=64-23,04\)
\(HC^2=40,96\)
\(\Rightarrow\)\(HC=\sqrt{40,96}=6,4\)
vậy \(y\)\(=\)\(6,4\)