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Mình giúp câu nào mình biết thôi nhé:v

1.D     3.B      4.C   5.A    6.Do chứa nhiều hạt sét

Câu 7 : B 

Câu 8 : C

Câu 9 : A 

Câu 10 : C 

Câu 11 : C

Câu 12 : B 

Câu 13 : D

Five years ago, I attended a very big festival in Ha Noi. It’s called 1000th Anniversary of Thang Long – Ha Noi Festival. There are a lot of activities in this festival such as fireworks display, military parade, music performances, ect. It was organized very splendidly because the organizers are the Viet Nam government. Millions of people came to Ha Noi to participate in this great festival. It was held for ten days from October 1st 2015 to October 10th 2015. I saw lots of fireworks, parties, parades during these days. It was interesting. I took so many pictures on this festival because there were plenty of beautiful scenes. We organized this great festival to celebrate the 1000th anniversary of Thang Long – Ha Noi.

x=2,5:(3/3,6)=...

Xét tam giác PMO và QNO có PMO=QNO=90 độ (gt) và POM=QON (2 góc đối đỉnh)

=>tam giác PMO đồng dạng QNO =>PM=QN=x=2,5 =)

20:

1: Xét ΔACD và ΔABE có

AC=AB

góc A chung

AD=AE

=>ΔACD=ΔABE

2: ΔABE=ΔACD

=>góc ABE=góc ACD

=>góc IBD=góc ICE

3: Xét ΔIBD và ΔICE có

góc IBD=góc ICE
BD=CE
góc IDB=góc IEC
=>ΔIBD=ΔICE

4: ΔIBD=ΔICE

=>IB=IC; ID=IE

=>ΔIBC cân tại I; ΔIDE cân tại I

không có câu hỏi sao trả lời

Câu 5:

a. $|x+\frac{4}{5}|-\frac{1}{7}=0$

$|x+\frac{4}{5}|=\frac{1}{7}$

$\Rightarrow x+\frac{4}{5}=\pm \frac{1}{7}$

$\Rightarrow x=\frac{-23}{35}$ hoặc $x=\frac{-33}{35}$

v.

$2x+5-(x-7)=18$

$2x+5-x+7=18$

$x+12=18$

$x=6$

c.

$2(x+1)+4^2=2^4$
$2(x+1)+16=16$

$2(x+1)=0$

$x+1=0$

$x=-1$

d.

$\frac{x-3}{x+5}=\frac{5}{7}$

$\Rightarrow 7(x-3)=5(x+5)$

$\Rightarrow 7x-21=5x+25$

$\Rightarrow 2x=46$

$\Rightarrow x=23$

Câu 5:

\(a,\left|x+\dfrac{4}{5}\right|-\dfrac{1}{7}=0\\ \Leftrightarrow\left|x+\dfrac{4}{5}\right|=\dfrac{1}{7}\\ \Leftrightarrow\left[{}\begin{matrix}x+\dfrac{4}{5}=\dfrac{1}{7}\\x+\dfrac{4}{5}=-\dfrac{1}{7}\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{7}-\dfrac{4}{5}\\x=-\dfrac{1}{7}-\dfrac{4}{5}\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{23}{35}\\x=-\dfrac{33}{35}\end{matrix}\right.\\ b,2x+5-\left(x-7\right)=18\\ \Leftrightarrow2x-x=18-5-7\\ \Leftrightarrow x=6\\ c,2\left(x+1\right)+4^2=2^4\\ \Leftrightarrow2\left(x+1\right)=2^4-4^2=16-16\\ \Leftrightarrow2\left(x+1\right)=0\\ \Rightarrow x+1=0\\ \Leftrightarrow x=0-1=-1\\ d,\dfrac{x-3}{x+5}=\dfrac{5}{7}\left(x\ne-5\right)\\ \Leftrightarrow7\left(x-3\right)=5\left(x+5\right)\\ \Leftrightarrow7x-21=5x+25\\ \Leftrightarrow7x-5x=25+21\\ \Leftrightarrow2x=46\\ \Leftrightarrow x=23\)

Câu 6:

b. Trung bình cộng các điểm: 

$\overline{x}=\frac{5.1+6.3+7.4+8.5+9.4+10.3}{20}=7,85$

Bài 13:

Ta có: a // b

\(\Rightarrow\widehat{G}=x=\left(180^o-138^o\right)+42^o=84^o\)

Bài 14:

Ta có: \(Cz\perp CB\) và \(By\perp CB\)

\(\Rightarrow Cz//By\)

Ta có:

\(\widehat{ABC}=\left(180^o-90^o\right)+\left(180^o-140^o\right)=90^o+40^o=130^o\) (đúng)

\(\Rightarrow Ax//By\)

14:

By vuông góc BC

BC vuông góc Cz

=>By//Cz

Gọi Bm là tia đối của tia By

=>góc mBC=90 độ

góc mBA=130-90=40 độ

góc mBA+góc BAx=180 độ

mà hai góc này trong cùng phía

nên Bm//Ax

=>By//Ax//Cz