Diện tích xung quanh là Sxq=2xhx(a+b)=2x3x(6+4)=60cm\(^2\)

kiến thức lớp 7 nha bn

B

Tự làm đi không làm được thì thôi đừng có đi tham khảo

\(\left|x-2\right|\left(x-1\right)\left(x+1\right)\left(x+2\right)=4\)

<=>\(\left|x-2\right|\left(x^2-1\right)\left(x+2\right)=4\)

<=>\(\left[{}\begin{matrix}\left(x-2\right)\left(x+2\right)\left(x^2-1\right)=4\\-\left(x-2\right)\left(x+2\right)\left(x^2-1\right)=4\end{matrix}\right.\)

<=>\(\left[{}\begin{matrix}\left(x^2-4\right)\left(x^2-1\right)=4\\\left(x^2-4\right)\left(x^2-1\right)=-4\end{matrix}\right.\)

<=>\(\left[{}\begin{matrix}x^4-5x^2+4=4\\x^4-5x^2+4=-4\end{matrix}\right.\)

<=>\(\left[{}\begin{matrix}x^4-5x^2=0\\x^4-5x^2+8=0\left(vô\right)lí\end{matrix}\right.\)

<=>\(x^2\left(x^2-5\right)=0\)

<=>\(\left[{}\begin{matrix}x=0\\x^2=5\end{matrix}\right.\)

<=>\(\left[{}\begin{matrix}x=0\\x=\pm\sqrt{5}\end{matrix}\right.\)

1. moved/ moving

-The film was so moving

-I was deeply moved by the film.

2. terrified/ terrifying

-Both of us were terrifyed of that violent scene.

-That violent scene was terrifying.

3. tired/ tiring

-Going shopping all day makes me feel tired.

-Going shopping all day is tiring.

4. interested/ interesting

-Jim’s interested in reading books.

-Jim finds reading books interesting.

5. fascinated/ fascinating

-Jane sometimes has many fascinating ideas.

-We are fascinated by Jane’s ideas.

6. depressed/ depressing

-The weather was depressing yesterday.

-The weather made me fell depressed yesterday.

7. annoyed/ annoying

-His tone of voice is so annoying

-I am so annoyed by his tone of voice.

8. shocked/ shocking

-His latest news was shocking.

-We were shocked at his latest news.

Cặp phân số bằng nhau là:\(\dfrac{8}{12}và\dfrac{14}{21}\)

Đồng dạng 1:\(10x^3y^2;-3x^3y^2;-5x^3y^2\)

Tổng :\(10x^3y^2+-3x^3y^2+-5x^3y^2=2x^3y^2\)

Đồng dạng 2:\(x^2y^3;\dfrac{1}{2}x^2y^3;-6x^2y^3\)

Tổng:\(x^2y^3+\dfrac{1}{2}x^2y^3+-6x^2y^3=\dfrac{-9}{2}x^2y^3\)

a)\(\sqrt{3}x-\sqrt{3}=\sqrt{3}\)

<=>\(\sqrt{3}x=2\sqrt{3}\)

<=>\(x=2\)

b)\(\left\{{}\begin{matrix}x+y=7\\-x+2y=2\end{matrix}\right.\)

<=>\(\left\{{}\begin{matrix}3y=9\\x+y=7\end{matrix}\right.\)

<=>\(\left\{{}\begin{matrix}x+3=7\\y=3\end{matrix}\right.\)

<=>\(\left\{{}\begin{matrix}x=4\\y=3\end{matrix}\right.\)

c)\(x^4-3x^2-4=0\)

<=>\(\left(x^2-4\right)\left(x^2+1\right)=0\)

<=>\(x^2-4=0\left(Vìx^2+1>0\forall x\right)\)

<=>\(x^2=4\)

<=>\(x=\pm2\)

Đăng rồi https://hoc24.vn/cau-hoi/bai-3-tinh-tong-va-hieu-cua-2-don-thuc-5xy2-va-3xy2.4723668481483