jimmmmmmmmmmmmmmmmmmmmmmmmmmm

he he he he he he

bài 1:

bn lấy giá trị của √(4^2-3,9^2) là dc

bài 2

AB+BC=2√(3^2+4^2)=??

Part 6 : 

1. especially

2. with

3. goods 

4. perform

Part 7: 

1. T

2. F

3. F

4.T

P6:

1. big

2. been

3. bought

4. people

P7:

1. T

2. F

3. F

4. F

Bài 18:

a: Ta có: \(P=\left(\dfrac{\sqrt{a}}{2}-\dfrac{1}{2\sqrt{a}}\right)^2\cdot\left(\dfrac{\sqrt{a}-1}{\sqrt{a}+1}-\dfrac{\sqrt{a}+1}{\sqrt{a}-1}\right)\)

\(=\dfrac{\left(\sqrt{a}-1\right)^2\cdot\left(\sqrt{a}+1\right)^2}{4a}\cdot\dfrac{a-2\sqrt{a}+1-a-2\sqrt{a}-1}{\left(\sqrt{a}+1\right)\left(\sqrt{a}-1\right)}\)

\(=\dfrac{\left(a-1\right)\cdot\left(-4\right)\cdot\sqrt{a}}{4a}\)

\(=\dfrac{-a+1}{\sqrt{a}}\)

b: Để P<0 thì -a+1<0

\(\Leftrightarrow-a< -1\)

hay a>1

c: Để P=-2 thì \(-a+1=-2\sqrt{a}\)

\(\Leftrightarrow-a+1+2\sqrt{a}=0\)

\(\Leftrightarrow a-2\sqrt{a}+1=2\)

\(\Leftrightarrow\left(\sqrt{a}-1\right)^2=2\)

\(\Leftrightarrow\sqrt{a}-1=\sqrt{2}\)

hay \(a=3+2\sqrt{2}\)

Bài 17:

a: Ta có: \(P=\dfrac{a\sqrt{a}-1}{a-\sqrt{a}}-\dfrac{a\sqrt{a}+1}{a+\sqrt{a}}+\left(\sqrt{a}-\dfrac{1}{\sqrt{a}}\right)\left(\dfrac{\sqrt{a}+1}{\sqrt{a}-1}+\dfrac{\sqrt{a}-1}{\sqrt{a}+1}\right)\)

\(=\dfrac{a+\sqrt{a}+1-a+\sqrt{a}-1}{\sqrt{a}}+\dfrac{a-1}{\sqrt{a}}\cdot\dfrac{a+2\sqrt{a}+1+a-2\sqrt{a}+1}{a-1}\)

\(=2+\dfrac{2a+2}{\sqrt{a}}\)

\(=\dfrac{2a+2\sqrt{a}+2}{\sqrt{a}}\)

Bài 1:

Gọi số cây 3 lớp 7A,7B,7C lần lượt là \(a,b,c\in \mathbb{N^*},cây\)

Áp dụng tc dtsbn:

\(\dfrac{a}{6}=\dfrac{b}{4}=\dfrac{c}{5}=\dfrac{a+b+c}{6+4+5}=\dfrac{30}{15}=2\\ \Rightarrow\left\{{}\begin{matrix}a=12\\b=8\\c=10\end{matrix}\right.\)

Vậy ...

Bài 3:

\(a+b\ne-c\Rightarrow a+b+c\ne0\\ \Rightarrow\dfrac{a+b-c}{c}=\dfrac{b+c-a}{a}=\dfrac{c+a-b}{b}=\dfrac{a+b+c}{a+b+c}=1\\ \Rightarrow\left\{{}\begin{matrix}a+b-c=c\\b+c-a=a\\c+a-b=b\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}a+b=2c\\b+c=2a\\c+a=2b\end{matrix}\right.\\ \Rightarrow P=\dfrac{a+b}{a}\cdot\dfrac{a+c}{c}\cdot\dfrac{b+c}{b}=\dfrac{2a\cdot2b\cdot2c}{abc}=8\)

Giúp mk với chiều nay phai nộp rùi

Diện tích mảnh vườn là

15x15=225(m²)

Trên cả mảnh vườn thu hoạch đc số kg cà chua là

10x(225:1)=2250(kg)

2250 kg cà chua

Cho xin một like đi các dân chơi à.

1.

1D 2C 3D 4B

2.

1A 2C 3C 4D 5D 6A

Câu 5:

\(VT=\dfrac{x^2yz}{xy+x^2yz+xyz}+\dfrac{y}{yz+y+xyz}+\dfrac{z}{xz+z+1}\\ =\dfrac{xz}{1+z+xz}+\dfrac{1}{z+1+xz}+\dfrac{z}{zx+z+1}\\ =\dfrac{zx+z+1}{zx+z+1}=1\)