Arrange the following sets of words to make meaningful sentences.

1. recycle / the environment./ bottles and cans / we will help / If we /

→ If we recycle bottles and cans, we wil help the the environment.

2. you / are / What / going to do / this weekend ?

→ What are you going to do this weekend ?

3. that / I / a hi - tech fridge / will have / can cook means.

→ I will have a hi-tech fridge that can cook means.

4. visited / We / our grandparents / in the countryside / last week.

→ We visited our grandparents in the countryside last weel.

c) (x+9).(x+7)= 143

Th₁: x+9 = 11                x+7=13

       x      = 2                  x    =6

Th₂: x+9 = 13                x+7=11

       x      = 4                  x    = 4

Th₃: x+9 = -11               x+7 = -13 

        x     = -20               x     = -20

Th_4: x+ 9 = -13               x+7= -11

       x       = -22               x    = -18

Bài 1:Tính nhanh

a,149+152+257+138 = 149 + 257 + ( 152 + 138 ) = 696

b,12.19.25 = ( 12.25 ).19 = 5700

c,79.37+79.18-55.78

= 79.(37+18) -55.78

= 79.55-55.78

=55.(79-78)

=55

Bài 2:Tìm x biết:

a,83+7.(25-x)=167

        7. (25-x)=167-83

        7. (25-x)=84

              25-x=84:7

              25-x=12

                   x=13

b,149-9.(x+12)=14

          9.(x+12)=149-14

          9.(x+12)=135

              x+12= 135:9

              x+12=15

              x      = 3

c,(x+9). (x+7)=143

\(\Leftrightarrow x+9=143\) hoặc \(x+7=143\)

 \(\Leftrightarrow x=134\)      hoặc \(x=136\)

Phân tử khối của Ca(HCO₃)₂ = 40+(1+12+16.3).2=162 đvC

\(=\sqrt[3]{2^3+3.2^2.\sqrt{3}+3.2.\left(\sqrt{3}\right)^2+\left(\sqrt{3}\right)^3}+\sqrt[3]{2^3-3.2^2.\sqrt{3}+3.2.\left(\sqrt{3}\right)^2+\left(-\sqrt{3}\right)^3}\)

\(=\sqrt[3]{\left(2+\sqrt{3}\right)^3}+\sqrt[3]{\left(2-\sqrt{3}\right)^3}=2+\sqrt{3}+2-\sqrt{3}=4\)

\(-2^3+2^2+\left(-1\right)^{2016}=-8+4+1=-3\)

bạn ơi, hình như đề này sai rồi thì phải 

Ta có : \(\frac{2x}{3}=\frac{3y}{4}=\frac{4z}{5}\Rightarrow\frac{12x}{18}=\frac{12y}{16}=\frac{12z}{15}\) và x+y+z = 49

Áp dụng tính chất của dãy tỉ số bằng nhau ta có :

\(\frac{12x}{18}=\frac{12y}{16}=\frac{12z}{15}=\frac{12\left(x+y+z\right)}{18+16+15}=\frac{12.49}{49}=12\)

Suy ra :

\(\frac{12x}{18}=12\Rightarrow x=18\)

\(\frac{12y}{16}=12\Rightarrow y=16\)

\(\frac{12z}{15}=12\Rightarrow z=15\)

Vậy x = 18, y=16, z=15

1.She (study)..studies.... maps in Geography.

2.Ba can (fix).fix.... the lights.

3.They (do).are doing.... some experiments at the moment.

4.You (be).will be...... a famous author one day.

5.We often (go).go..... to the club after school

6.He enjoy (draw).drawing..... picture.