Question

[kaido]

Cau 1 : cho 3 duong thang doi 1 cat nhau tao thanh 3 giao diem phan biet .Hoi co bao nheu tia co goc la 1trong 3 giao diem do
Cau 2: Ve n tia phan biet chung gốc  . Biet rang tren hinh co 36 góc .Tìm n
Cau 3: tim p/s bang 20/39 .Biet UCLN cu tu va mau nau bang 36
Cau 4 : Tap hop gia tri x thoa man |x+3|+|x+4|=1
Cau 5: Trong 1 buoi giao luu van nghe , h/s nu chiem 2/5 ,trong do co 3/8 la h/s lop 6.Trong so h/s nam co 2/9 la hoc sinh lop 6. Tinh so h/s lop 6 .Biet so h/s trong khoang tu 130 den 200
Cau 6: ti so cu hai so bang 2:7 neu them 35 vao so thu 1 thi ty so giua 2 so =11:14. Tinh so > hon
Cau 7 : So phan tu cua tap hop x thoa man

11-x+|x+2|=0
cau 8: 1 o to di quang duong AB voi van toc 40km/h luc ve di voi van toc 50 km/h . Time ca di lan ve =4h30 .tinh AB
Cau 9 : Can it nhat bao nhieu diem de khi noi lai ta duoc 4hinh tam gia    

Minh viet tat nen hoi kho doc
ban nao giai duoc bao nhieu cau thi duoc bay nhieu tick
 

Answer 1

[Đông Phương Lạc]

Câu 4: \(\left|x+3\right|+\left|x+4\right|=1\)

Ta có: \(\left|x+3\right|\ge0\forall x\) và \(\left|x+4\right|\ge0\forall x\)

Nên: \(\left|x+3\right|+\left|x+4\right|=1\)

\(\Leftrightarrow\hept{\begin{cases}\left|x+3\right|=0\\\left|x+4\right|=1\end{cases}}\)

Ta có: \(\left|x+3\right|=0\)

\(\Leftrightarrow x+3=0\)

\(\Leftrightarrow x=0-3\)

\(\Leftrightarrow x=-3\) \(\left(1\right)\)

Lại có: \(\left|x+4\right|=1\)

\(\Leftrightarrow\orbr{\begin{cases}x+4=1\\x+4=-1\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}x=1-4\\x=-1-4\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}x=-3\\x=-5\end{cases}}\) \(\left(2\right)\)

Từ \(\left(1\right)\) và \(\left(2\right)\) suy ra: \(x=-3\)

Vậy: \(x=-3\)

Answer 2

[Đông Phương Lạc]

Câu 7:

 \(11-x+\left|x+2\right|=0\)

\(\Leftrightarrow11-x=-\left|x+2\right|\)

\(\Leftrightarrow-\left(11-x\right)=\left|x+2\right|\)

\(\Leftrightarrow-11+x=\left|x+2\right|\)

\(\Leftrightarrow\orbr{\begin{cases}-11+x=x+2\\-11+x=-\left(x+2\right)\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}-11-2=x-x\\-11+x=-x-2\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}-13=0\\x+x=-2+11\end{cases}}\)( T/h 1 vô lí )

\(\Leftrightarrow2x=9\)

\(\Leftrightarrow x=9:2\)

\(\Leftrightarrow x=\frac{9}{2}\)

P/s: Chắc sai =))