\(a,=\left(6x+1-6x+1\right)^2=4\\ b,=3x^2-6x-5x+5x^2-8x^2-24=-11x-24\\ c,=14x^2+x-3-5x^2-18x+8-9x^2+17x=5\\ d,=6x^2+43x-40-6x^2-7x+3-36x+27=-10\)

a) \(=\left(6x+1\right)^2-2\left(6x+1\right)\left(6x-1\right)+\left(6x-1\right)^2=\left(6x+1-6x+1\right)^2=2^2=4\)

b) \(=3x^2-6x-5x+5x^2-8x^2+24=-11x+24\)

c) \(\left(7x-3\right)\left(2x+1\right)-\left(5x-2\right)\left(x+4\right)-9x^2+17x=\left(7x-3\right).2x+\left(7x-3\right)-\left[\left(5x-2\right).x+4\left(5x-2\right)\right]-9x^2+17x=14x^2-6x+7x-3-\left(5x^2-2x+20x-8\right)-9x^2+17x=5x^2+18x-3-\left(5x^2+18x-8\right)=5x^2+18x-3-5x^2-18x+8=5\)

d) \(\left(6x-5\right)\left(x+8\right)-\left(3x-1\right)\left(2x+3\right)-9\left(4x-3\right)=\left(6x-5\right).x+8\left(6x-5\right)-\left[\left(3x-1\right).2x+3\left(3x-1\right)\right]-36x+27=6x^2-5x+48x-40-\left(6x^2-2x+9x-3\right)-36x+27=6x^2+7x-13-\left(6x^2+7x-3\right)=6x^2+7x-13-6x^2-7x+3=-10\)

a: Ta có: \(8x\left(x-2017\right)-2x+4034=0\)

\(\Leftrightarrow\left(x-2017\right)\left(4x-1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=2017\\x=\dfrac{1}{4}\end{matrix}\right.\)

c: Ta có: \(4-x=2\left(x-4\right)^2\)

\(\Leftrightarrow2\left(x-4\right)^2+x-4=0\)

\(\Leftrightarrow\left(x-4\right)\left(2x-7\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=4\\x=\dfrac{7}{2}\end{matrix}\right.\)

a) ta có AD vg góc DC

            BC vg góc DC

             EG vg góc DC

=> AD//BC//EG

Xét tg ABCD có AD//BC=> ABCD là hình thang

Xét hình thang ABCD có EG //BC//AD

                                        AE= EB (gt)

=> G là td DC (EG là dg tb hthang ABCD)

=> DG=GC=5cm=> X =5 cm

b) Thêm dk là HI//OJ//NK//M...

Xét tg HINK có HI//NK(gt) => HINK là hthang 

Xét Hthang HINK có OH =ON (gt)

                                  IJ=IK(gt)

=>OJ là dg tb hình thang HINK

=> OJ= (HI+NK):2=(8+16):2=12 cm=> x=12 cm

Xét tg OJM... có OJ//M.. => OJM.. là hình thang

(cmt tương tự như ở trên)

=> M..= NK.2-OJ=16.2-12=20 cm

Bạn xem lại chỗ .... là gì nhé!

a, văng vẳng, quang quác quác, tè te te

Tác dụng: Cho thấy sự huyên náo của các loài vật trong rừng núi, nó làm bức tranh thiên nhiên trở nên sinh động và đẹp hơn

b, đùng đùng, vù vù, lộp độp

Tác dụng: Cho thấy những dấu hiệu trước cơn mưa, cơn mưa diễn ra nhanh chóng và mạnh 

a: \(4x^2-6x=2x\left(2x-3\right)\)

b: \(9x^4y^3+3x^2y^4=3x^2y^3\left(3x^2+y\right)\)

c: \(x^3-2x^2+5x=x\left(x^2-2x+5\right)\)

d: \(3x\left(x-1\right)+5\left(x-1\right)=\left(x-1\right)\left(3x+5\right)\)

e: \(2x^2\left(x+1\right)+4\left(x+1\right)=2\left(x+1\right)\left(x^2+2\right)\)

f: \(-3x-6xy+9xz=-3x\left(1+2y-3z\right)\)

Bài 1.

a, PTPƯ: kẽm + axit clohidric → kẽm clorua + hidro

b, Theo ĐLBTKL ta có:

 \(m_{Zn}+m_{HCl}=m_{ZnCl_2}+m_{H_2}\)

c, Ta có: \(m_{HCl}=m_{ZnCl_2}+m_{H_2}-m_{Zn}=27,2+0,4-13=14,6\left(g\right)\)

Bài 2:

a, PTPƯ: metan + oxi → cacbon dioxit + hơi nước

b, Theo ĐLBTKL ta có: 

 \(m_{CH_4}+m_{O_2}=m_{CO_2}+m_{H_2O}\)

c, Ta có: \(m_{O_2}=m_{CO_2}+m_{H_2O}-m_{CH_4}=132+108-48=192\left(g\right)\)  

 PT chữ: Metan + Oxi \(\xrightarrow[]{t^o}\) Cacbon đioxit + Nước

Bảo toàn khối lượng: \(m_{O_2}=m_{CO_2}+m_{H_2O}-m_{CH_4}=192\left(g\right)\)

Bài 1:

PT chữ: Kẽm + Axit clohidric \(--->\) Kẽm clorua + Hidro

Bảo toàn khối lượng: \(m_{HCl}=m_{ZnCl_2}+m_{H_2}-m_{Zn}=14,6\left(g\right)\)

Câu 2

\((1) MnO_2 + 4HCl \to MnCl_2 + Cl_2 + 2H_2O\\ (2) Cl_2 + H_2 \xrightarrow{as} 2HCl\\ (3) 3Cl_2 + 2Fe \xrightarrow{t^o} 2FeCl_3\\ (4) 2FeCl_3 + Fe \to 3FeCl_2\\ (5) 2NaOH + Cl_2 \to NaCl + NaClO + H_2O\)

\((1) 4Al + 3O_2 \xrightarrow{t^o} 2Al_2O_3\\ (2) 2Fe + 3Cl_2 \xrightarrow{t^o} 2FeCl_3\\ (3) C + O_2 \xrightarrow{t^o} CO_2\\ (4) 2KMnO_4 \xrightarrow{t^o} K_2MnO_4 + MnO_2 + O_2\\ (5) 4P + 5O_2 \xrightarrow{t^o} 2P_2O_5\\ (6) 2KClO_3 \xrightarrow{t^o} 2KCl + 3O_2\\ (7) Fe + H_2SO_4 \to FeSO_4 + H_2\\ (8) Cu + 2H_2SO_4 \to CuSO_4 + SO_2 + 2H_2O\\ (9) 2Fe + 6H_2SO_4 \to Fe_2(SO_4)_3 + 3SO_2 + 6H_2O\\ (10) 2Al + 6H_2SO_4 \to Al_2(SO_4)_3 + 3SO_2 + 6H_2O\)

Bài 5: 

1. There are a few students taking part in the event     

→ There aren't many students taking part in the event.

2. If he doesn't work hard, he will lose his job     

→ Unless he works hard, he will lose his job.

3. Let's write about the three Rs ?         

→ Why  don't we write about the three Rs?

4. Learning about recyking is fun           

→ It's fun to learn about recycling.

5. It's not good to throw old clothes away               

→ You  shouldn't throw old clothes away

Xếp từ thành câu

Bài 1

1. they / to / movies / do / how / go / the / often ?   

→ How often do they go to the movies?

2. your eyes / swimming / should / when  goggles / you / you / go / wear / to protect

→ When you go swimming, you should wear goggles to protect your eyes.

3. usually / his  / swimming / with / friends / he / goes       

→ He usually goes swimming with his friends.

4. go / do / weekend / on / always / fishing / parents / their ?   

→ Do their parents always go fishing on the weekend?

5. camping / they / go / do / sometimes

→  Sometimes they go camping.

6. what / TV / you / do / on / sports / watch?

→ What sports do you watch on TV?

Bài 2

1. Our / important / an / sports and games / in play / lives / part       

→ Sports and games play an important part in our lives.       

2. players / how / match / there / in / many / are / football / a ?   

→ How many players are there in a football match?

3. by / she / to keep / every day / tries / fit / jogging 

→ She tries to keep fit by jogging every day.

4. yesterday / who / play / football / you / did / with ?

→ Who did you play football with yesterday?

5. sports / building / physical and strength / necessary / are / for

→ Sports are necessary for building physical strength.

6. to switch / before / go / don't / the TV / off / you / forget / to bed

→ Don't forget to switch off the TV before you go to bed.

7. Sunday / I / usually / friends / swimming / on / go / mornings / with / my

→ On Sunday mornings, I usually go swimming with my friends.

8. match / you / on / the / did / television / last night / watch / basketball / the ?

→ Did you watch the basketball match on television last night? 

2 should not go out for a walk

3 will quit it at once

4 must buy a smaller one

5 may be very worried

6 may find another one

7 can understand the lecture well

8 has to leave the building in order

9 ought to come to visit me more

10 must be very happy