`A = (2x+y)^2 - (2x-y)^2`
`-> A = 4x^2 + 4xy + y^2 - ( 4x^2 - 4xy + y^2)`
`-> A = (4x^2 - 4x^2) + (4xy + 4xy) + (y^2-y^2)`
`-> A = 8xy`
$\\$
`B = (x-2y)^2 - 4(x-2y)y + 4y^2`
`-> B = x^2 - 4xy + 4y^2 - 4xy + 8y^2 + 4y^2`
`-> B = x^2 + (-4xy - 4xy) + (4y^2 +4y^2+ 8y^2) `
`-> B = x^2 - 8xy + 16y^2`
Đáp án + Giải thích các bước giải:
`A=(2x+y)^{2}-(2x-y)^{2}`
`=(2x+y+2x-y)(2x+y-2x+y)`
`=4x.2y`
`=8xy`
``
`B=(x-2y)^{2}-4(x-2y)y+4y^{2}`
`=(x-2y)^{2}-2.(x-2y).2y+(2y)^{2}`
`=(x-2y-2y)^{2}`
`=(x-4y)^{2}`
I. 1. We ___ British, we’re American. 2. "What’s that?" "It’s ___ identity card." 3. ___ your teacher live in London? 4. I usually get up late ___ Sundays. 5. I ___ sing, but I can play the guitar. 6. This bag’s ___. Look! It’s got my name on it. 7. Is ___ any milk in the fridge? 8. I’m taller __ my brother. 9. "Would you like to fly a plane?" "No, I ____." 10. I hardly ___ watch TV at the weekend. 11. _____ were a lot of people at the cinema last night. 12. It’s the ___ interesting book I’ve ever read. 13. "How much coffee do you drink?" "Quite a ___." 14. "What’s the time?" "It’s half ___ three." 15. They ___ like the film – they left after 10 minutes. 16. I spoke to him on the phone ten minutes ____. II. 1. She’s my childrens’ / children’s teacher. 2. I have always / I always have breakfast at home. 3. They’re beautiful flowers / flowers beautiful. 4. I don’t like get up / getting up early. 5. We don’t have some / any money. 6. Please drive careful / carefully. The weather’s bad. 7. Can we meet on / in Monday evening? 8. My father’s doctor / a doctor. 9. I have a lot of / a lot brothers and sisters. 10. "Is that his umbrella?" "No, it’s ours / our." III. 1. Simon ___ (not be) at work yesterday. 2. I ___ (buy) a new car last week. 3. My sister ___ (listen) to music at the moment. 4. We ___ (not have) a holiday next year. 5. Where ___ (be) he yesterday morning? 6. ____ you ever ___ (break) your leg? 7. I ____ (not be) to France. Is it nice? 8. They ____ (not drive) to London – they got the train. 9. __ she ___ (have) a party next week? 10. Who ___ (be) the three greatest politicians of the twentieth century? 11. He has an exam tomorrow, so he ___ (study) now. 12. She ___ (not like) writing postcards. 13. How often ___ you __ (use) your mobile? 14. Emma ___ (write) him a letter two days ago. IV. 1. I sometimes have an e___ for breakfast. 2. I must buy a new w____. I’m always late for work! 3. I gave my brother a w___ for his birthday last year. He often loses his money. 4. I usually have s___ for lunch. I love bread. 5. I want to write something – can I borrow your p___, please? 6. I have a c___ at home but I don’t use it very often. I check my emails at work. 7. I was late for work because the b____ was late. 8. I read the n___ every day. 9. She’s listening to the news on the r___. 10. I read two b___ when I was on holiday last summer.
Cho e hỏi đến đó làm sao cho ra n đc ạ
Cho tam giác ABC cân tại A . Gọi M , N , H lần lượt là trung điểm của AB , AC , BC a , Chứng minh tứ giác MNCB là hình thang cân b , Gọi D là điểm đối xứng của H qua N . Các tứ giác AHCD , ADMN là hình gì ? Vì sao ? c , Chứng minh N là trọng tâm của tam giác CMD d , MD cắt AC tại E . Chứng minh BN đi qua trung điểm của HE .
anh chị nào giúp em với hưa vote năm sao
Giải thích và chọn đáp án giúp mình vs
tính : A= 1/6 - 1/35 - 1/63 - 1/99 - 1/143 - 1/195
Mình đang cần gấp mình sẽ cho 5 sao
Tính bằng cách thuận tiện nhất: 1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56
Nhờ các bạn cách nào hợp lý nhất
E= 5x^2 -7xy -24y^2. Mn giải giúp e vs ạ ghi cách giải cụ thể nha
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