làm mỗi bài 7.2.11b thôi
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XI
1, than
2, whole
3, in
4, much
5,on
6, is
7, surface
8, to
9, word
10, mile

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

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


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

d) \(xy+5x-7y=35\)
\(\Leftrightarrow\left(xy+5x\right)-\left(7y+35\right)=0\)
\(\Leftrightarrow\left(y+5\right).\left(x-7\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-7=0\\y+5=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=7\\y=-5\end{matrix}\right.\)