Ta có \(a=12x+8\)

Để thương tăng lên 2 đơn vị thì

 \(a=12\left(x+2\right)+8\)

\(\Leftrightarrow a=12x+32\)

⇒ a tăng thêm 32-8=24 đơn vị để thỏa mãn yêu cầu

còn câu d đang suy nghĩ

A B C E D K H

a) Áp dụng định lí Pytago:

\(BH=\sqrt{AB^2-AH^2}\)

\(\Rightarrow BH=6cm\)

 b) Xét tam giác ABH và tam giác ACH có:

+AH: cạnh chung

+AB=AC (ΔABC cân tại A)

⇒ ΔABH = ΔACH (ch-cgv)

c)Ta có ΔABH = ΔACH (CMT)

⇒BH=CH

Mà DH ⊥ BC tại trung điểm H.

⇒ ΔBDH = ΔCDH.

⇒BD=DC 

Mà BD=DE ⇒DE=DC

⇔AD+DE=AD+DC >AC (ĐPCM).

Điều kiện:

\(\Delta=\left(m^2+1\right)^2-4\left(m^2-7m+12\right)>0\)

\(\Leftrightarrow m^4+2m^2+1-4m^2-28m+48>0\)

\(\Leftrightarrow m^4-2m^2-28m+49>0\)

rồi giải ra m nhá 

đề thiếu nhé

Exercise 1. Put the correct prepositions in the blanks for combination with GET 

Get away from Get down Get on / along with Get off Get into Get away with Get down to Get over Get off with Get back Get on Get out of Get through 1.He promised to act as chairman, so I’m afraid he can’t get ____ it now. There’s no one else to do it. 2.She is a friendly girl who gets ________ everyone she meets. 3.It took her a long time to get ______ the death of her husband. 4.I tried to ring him up but I couldn’t get _____ : I think some of the lines are down after last night’s storm. 5.She talks so much that it is difficult to get _______ from her. 6.Get ______ the bus at Victoria Station. 7.How are you getting _________ your work ? 8.I’m not getting _______ very fast because I can only type with two fingers. 9.We got ______ late because we missed the last train. 10.Don’t worry about my snake. He can’t get _______ his box. 11.This rainy weather is really getting me ________. 12.It’s time you got _______ some serious work. It’s very important to you. 13.Thieves raided the bank and got ________ a lot of money. 14.My boy is getting _________ bad habits, such as smokin, staying up late.... 15.We got _______ immediately after the breakfast. 

Exercise 2. Put the correct prepositions in the blanks for combination with GIVE 

Give away Give off Give over to Give up Give back Give out Give in Give oneself up 1.He won 100$ and gave it all ________. 2.Riding is getting too expensive: I’ll have to give it ________. 3.He gave _______all the books he had borrowed. 4.After 4 days of freedom, the escaped prisoner gave himself _______ to local police. 5.Your secret is safe with me. I won’t give it ________. 6.The diver’s supply of oxygen gave __ and he had to be brought to the surface as quickly as possible 7.After his fourth attemp he gave _______ trying to pass the driving test. 8.If you want to save money, give _______ eating in expensive restaurants. 9.There was a man giving _______ leaflets outside the church. 10.She gave ______ state secret to the enemy. 11.Could you give me _______ my pen when you’ve finished using it? 12.Please give your exam papers ______ to the teacher when you’ve finished! 13.The cooker is giving _______ a funny smell. 14.This big hall is given ________ meeting. 15.She’s a gusty player : she never gives __________ 

Exercise 3. Put the correct prepositions in the blanks for combination with GO

 Go away Go down with Go on Go out Go through with Go back on Go in for Go off Go round Go up Go down Go into Go over Go through Go with 1.The guard dog went ______ the intruder and knocked him down. 2.He had a sandwich and a cup of coffee, then went _______ working. 3.I went ______ the proposal very carefully with my lawyer and finally decided to to accept his offer. 4.She went ______ a beauty contest and got a prize. 5.The price of tomatoes usually goes ________ in summer in England. 6.If there isn’t enough soup to go ________, just put some hot water in it. 7.You can’t go _______ your promise now: we are depending on you. 8.They have gone _______ all the calculations again but they still can’t find the mistake. 9.The gun went ______ by accident and wounded him in the leg. 10.Mary went ______ in such a hurry that she left her passport behind. 11.Why don’t you go _______ stamp collecting if you want a quiet hobby ? 12.Her weight went ______ to 70 kilos when she stopped playing tennis. 13.When did Britain go ________ EEC ? 14.Our youngest boy has gone __________ mumps! 15.Her blouse doesn’t go _______ her skirt. 16.Finally, I’ve gone ________ all my exams! 17.Which events is he going __________ at the Olympics? 18.The first episode of the film goes ________ next Friday evening at 8 o’clock. 19.There must be a party going _______ next door. They’re making so much noise! 20.The thieves ran away when the burglar alarm went __________. 

Exercise 4. Put the correct prepositions in the blanks for combination with HAND, GROW, HANG, JUMP 

Grow on Grow up Hand down Hang about Hang on to Jump at Grow out of Hand over Hand out Hang back Jump on 1.Most of my clothes were handed _____ to me by my older brother. 2.President Bush should hand ______ power to Iraqui elected government. 3.Relief workers were handing _______ emergency rations to the survivors. 4.My daughter is growing _______ very fast. She has grown _______ all her clothes. 5.This book is very interesting. I’m sure it will grow ________ you. 6.You should keep an eye on this stranger. He has been hanging _____ our neighbourhood for hours. 7.At first, he volunteered to help me, but on second thought he was afraid and hung ______. 8.I should hang ______ those oldphotographs–they may be valuable. 9.My maths teacher really used to jump _____ us when we got our answer wrong. 10.If they offered me a job in the USA, I’d jump _______ the chance. 

Exercise 5. Put the correct prepositions in the blanks for combination with HOLD, KEEP 

Hold on Hold out Hold up Keep down Keep away Keep off Hold off Hold back Hold with Keep up with Keep back Keep up 1.“ What a terrible news!”, she just managed to hold _________ her anger. 2.I don’t hold _______ his view on education. 3.After the hold–_______, the gang made their getaway in a stolen car. 4.The survivors of the plane crash managed to hold _______ till help came. 5.Her illness is getting worse. Doctors hold ______ little hope of her recovery. 6.Could you hold ______ making decision until next week. I’m trying to find out the best solution. 7.She kept ______ working although she was very tired. 8.They lit a fire to keep wild animals __________. 9.The people in this country have been kept _______ for years by a brutal regime. 10.Keep your voices ________ : your mother is trying to get some sleep. 11.You’re all doing a spendid job. Keep _______ the good work. 12.Police warned by–standers to keep ________ from the blazing building. 13.I can’t keep ________ all the changes in computer technology. 14.She is a good secretary, but she is kept _______ by her ignorance of languages. 15.The country was in a state of rebellion and was only kept _______ by repressive measures. 

Exercise 6. Put the correct prepositions in the blanks for combination with LAY, LEAVE, LET, LIVE

 Lay down Lay up Leave out Let off (with) Live on Lay out Leave off Let down Let out Live up to 1.There is a lot of beautiful jewellery laid _______ in the shop window. 2.You should lay _______ some money in the rainy days. 3.You didn’t have any right to lay _______ such hard rules. 4.My name has been misspelt–you’ve left _______ a letter. 5.I wish you’d leave ________ complaining about my cooking. 6.The boy’s getting so fat that his trousers have to be let _____ round the waist. 7.She was let _______ with a fine instead of being sent to prison. 8.He felt he really let the team ________ when he missed the penalty. 9.Don’t let these criminals ________ lightly. 10.As he’s retired, he now lives mainly _________ his pension. 11.My exam results didn’t live _________ my expectations, 12.You can’t live ________ 22 calories a day. 

Exercise 7. Put the correct prepositions in the blanks for combination with LOOK

 1.We are looking ____ you for your help. 2. We must look __ a bit before deciding where to buy a house 3. Police will be looking _ trouble–makers at today’s match. 4. Please look __ on me when you have free time 5.His disappearance is being looked _________ by the police. 6. Do look me __ the next time you’re in London. 6. Children always look _____ their parents. 8. She is looked __ as the leading authority on this subject 9.Who will look ______ the children while their mother is in hospital ? 10.We are so much looking __________ seeing you next week. 11.Look _______ the time of the next trainin the timetable. 12.He was looked _________ because of his humble background. 13.She looked _______ when she heard the noise behind her. 14.Tenants must look __________ the house before they decided to rent it. 

GIẢI NHANH MÌNH TICK CHO NHA

\(1+1=2\)

12000000*(1+0.6%)*(1+0.6)=12144432 (dong)

Chac chan 100%

600 số