Lời giải:
Đặt $xy=k$. Ta có:

$x_1y_1=k=x_2y_2$

Thay $x_1=6; x_2=-9\Rightarrow 6y_1=-9y_2$

$\Leftrightarrow y_1=-1,5y_2$

$y_1-y_2=10$

$-1,5y_2-y_2=10$

$-2,5y_2=10$

$y_2=-4$

$y_1=-1,5y_2=-1,5.(-4)=6$

\(11,\\ a,M=\dfrac{1+\sqrt{a}}{\sqrt{a}\left(\sqrt{a}-1\right)}\cdot\dfrac{\left(\sqrt{a}-1\right)^2}{\sqrt{a}+1}=\dfrac{\sqrt{a}-1}{\sqrt{a}}\\ b,M=\dfrac{\sqrt{a}-1}{\sqrt{a}}=1-\dfrac{1}{\sqrt{a}}< 1\left(\dfrac{1}{\sqrt{a}}>0\right)\)

\(9,\\ a,=\left|2-\sqrt{7}\right|=\sqrt{7}-2\\ b,=5\sqrt{3}+4\sqrt{3}-10\sqrt{3}=-\sqrt{3}\\ c,=3-4+2=1\\ d,=6\sqrt{3a}-4\sqrt{3a}=2\sqrt{3a}\\ 10,\)

a, Áp dụng HTL: \(x=\sqrt{9\cdot25}=15\)

b, Áp dụng HTL: \(\left\{{}\begin{matrix}8^2=10x\\y^2=x\left(x+10\right)\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=6,4\\y=\sqrt{6,4\cdot16,4}\approx10,245\end{matrix}\right.\)

câu mấy với câu mấy

ko biết lm

1, That
2, This
3, that
4, those
5, these - that
6, these
7, this
8, that
9, that
10, this
11, those
12, this
13, it
14, these
15, them

16, those

this/that dùng cho ng, vật số ít

this: dùng cho ng, vật ở gần

that: dùng cho ng, vật ở xa

these/those dùng cho ng, vật số nhiều

these: ở gần

those: ở xa

my - your
my
I - my
her
Nam and Lan's teacher
is
Her
Those students' school bags
your
He
is - your - She
its
her
His
their
hers
him
her

1 my/your

2 my

3I/my

4 her

5 Nam and Lan's teacher

6 is./Her

7 Those students' school bags

8 your/He

9 is/your/she

10 its

11 Her

12 His

13 their

14 hers

15 him

16 her

1 friendly

 2 creative

3 boring

4 funny

5 sensitive

6  outgoing

7 lazy

8 impatient

9 active

10 quiet

1.Yes, they do

2..Yes, it is

3.People buy fruits and flowers from the market and decorate their house

4.People visit their family and friends