=(9/25 + 16/25) + ( 2/11 + 9/11)+ (10/17 + 7/17)

= 1    +     1       +          1

= 3

Toán này đâu khó!

1=1=1=3

a)\(5x^2.\left(10x^4-5x^3+2\right)=50x^6-25x^5+10x^2\)

b) \(\left(x^2-5x+3\right).\left(-5x\right)=-5x^3+25x^2-15x\)

c) \(\left(5x-2y\right)\left(x^2-xy+1\right)=5x^3-5x^2y+5x-2x^2y+2xy^2-2y\\ =5x^3-7x^2y+2xy^2+5x-2y\)

d) \(\left(3x-2\right)\left(9x^2+6x-4\right)\\ =27x^3+18x^2-12x-18x^2-12x+8=27x^3+8\)

a) \(5x^2\left(10x^4-5x^3+2\right)=50x^6-25x^5+10x^2\)

b) \(\left(x^2-5x+3\right)\left(-5x\right)=-5x^3+25x^2-15x\)

c) \(\left(5x-2y\right)\left(x^2-xy+1\right)=5x^3-5x^2y+5x-2x^2y+2xy^2-2y=5x^3-7x^2y+2xy^2+5x-2y\)

d) \(\left(3x-2\right)\left(9x^2+6x-4\right)=27x^3+18x^2-12x-18x^2-12x+8=27x^3-24x+8\)

1 That exercise is more difficult this one

2 The red car is more expensive than the black one

3 That film is not as exciting as this one

4 That river is shorter than this one

5 Miss Nga is younger than Miss Lan

6 Your kitchen is bigger than mine

7 Her new house is smaller than her old one

8 The white dress is cheaper than the blacj one

9 According to me, Maths is more difficult than English

10 That computer can't work as well as this one

Câu 2: Ta có :\(v=\dfrac{\Delta C}{\Delta t}\)

=> Tốc độ trong thời gian đó là: \(v=\dfrac{0,024-0,022}{10}=0,0002\) mol/l.s.

Đây là bài lớp 7 mà nhưng mik mới hc lớp 6 sr nha

Bài 2:

Bài 3:

A B C x y

Vì BC và Cx là 2 tia đối nên \(\widehat{BCA}\) và \(\widehat{ACx}\) là 2 góc kề bù

\(\Rightarrow\widehat{ACB}+\widehat{ACx}=180^o\)

     \(40^o+\widehat{ACx}=180^o\)

     \(\widehat{ACx}=140^o\)

b) Ta có:\(\widehat{ACB}+\widehat{ABC}+\widehat{BAC}=180^o\) (tổng 3 góc trong 1 tam giác)

             ​​​\(40^o+\widehat{ABC}+70^o=180^o\)​

            \(\widehat{ABC}=70^o\)(1)

Vì Oy là phân giác của \(\widehat{ACx}\) nên \(\widehat{xCy}=\dfrac{\widehat{ACx}}{2}=\dfrac{140^o}{2}=70^o\)(2)

Từ (1),(2) => \(\widehat{ABC}=\widehat{xCy}\)

c)Cặp góc đồng vị là \(\widehat{ABC}\) và \(\widehat{xCy}\)