làm mỗi bài 7.2.11b thôi
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![](https://rs.olm.vn/images/avt/0.png?1311)
XI
1, than
2, whole
3, in
4, much
5,on
6, is
7, surface
8, to
9, word
10, mile
![](https://rs.olm.vn/images/avt/0.png?1311)
is having
has
takes
to stay
drinks
is eating
is
speaks
has been
has visited
is having
has
takes
to stay
drinks
is eating
is
speaks
has been
has visited
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 2:
a: \(x^2+6x+9=\left(x+3\right)^2\)
b: \(4x^2+4x+1=\left(2x+1\right)^2\)
c: \(4x^2-12xy+9y^2=\left(2x-3y\right)^2\)
d: \(x^4-4x^2+4=\left(x^2-2\right)^2\)
Bài 3:
a: \(\left(x-2\right)\left(x^2+2x+4\right)-\left(x^3+2\right)\)
\(=x^3-8-x^3-2\)
=-10
b: \(\left(x+4\right)\left(x^2-4x+16\right)-\left(x-4\right)\left(x^2+4x+16\right)\)
\(=x^3+64-x^3+64\)
=128
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 6:
a) Vì $D$ là trung điểm $AC$ nên $AD=DC$. Do đó:
\(\frac{S_{ABD}}{S_{BDC}}=\frac{AD}{DC}=1\)
$\Rightarrow S_{ABD}=S_{BDC}$
b) Ta có: $EC<BC\Rightarrow \frac{EC}{BC}<1$
$\frac{S_{AEC}}{S_{ABC}}=\frac{EC}{BC}<1$
$\Rightarrow S_{AEC}<S_{ABC}$
c) Mình nghĩ lớp 5 chưa đủ kiến thức để làm câu này
![](https://rs.olm.vn/images/avt/0.png?1311)
d) \(xy+5x-7y=35\)
\(\Leftrightarrow\left(xy+5x\right)-\left(7y+35\right)=0\)
\(\Leftrightarrow\left(y+5\right).\left(x-7\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-7=0\\y+5=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=7\\y=-5\end{matrix}\right.\)
![](https://rs.olm.vn/images/avt/0.png?1311)