X^2+1/x+1 + x^2+2/x-2=-2
4 phút trước
ai giải giúp mình ví dụ 2 với ạ
9 phút trước
`(x-3)^3 - (x-3)(x^2 + 3x+9)+9(x+1)^2=15`
`=> x^3 - 9x^2 + 27x - 27 - (x^3 - 3^3) + (3x + 3)^2 =15`
`=> x^3 - 9x^2 + 27x - 27 - x^3 + 27 + 9x^2 + 18x + 9 = 15`
`=> (x^3 - x^3) + (-9x^2 + 9x^2) + (27x + 18x) + (-27+27 + 9)=15`
`=> 45x + 9 = 15`
`=> 45x=6`
`=> x=6/45`
`=>x=2/15`
Vậy: `x=2/15`
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11 phút trước
cho mik xin hình bài này ạ
cả nhà ơi cho e hỏi là cho tam giác ABC có AB=3 , AC=4 , góc A = 120 độ
a) tính BC
b) tính góc B , C
c) diện tích của tam giác ABC
giúp e với ạ e cảm ơn anh chị :>
a)
Áp dụng ĐL cosin cho \(\Delta ABC\) có:
\(BC^2=AB^2+AC^2-2AB\cdot AC\cdot cos120^o\)
\(BC=\sqrt{3^2+4^2-2\cdot3\cdot4\cdot\left(-\dfrac{1}{2}\right)}=\sqrt{37}\)
b)
Áp dụng hệ quả ĐL cosin cho \(\Delta ABC\) có:
\(cosB=\dfrac{AB^2+BC^2-AC^2}{2\cdot AB\cdot AC}\)
\(cosB=\dfrac{3^2+\sqrt{37}^2-4^2}{2\cdot3\cdot\sqrt{37}}=\dfrac{5\sqrt{37}}{37}\)
\(\Rightarrow\widehat{B}\approx35^o\)
\(\Rightarrow\widehat{C}=180^o-120^o-35^o=25^o\)
c)
\(S_{ABC}=\dfrac{1}{2}AB\cdot AC\cdot sin120^o=\dfrac{1}{2}\cdot3\cdot4\cdot\dfrac{\sqrt{3}}{2}=3\sqrt{3}\)
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Cho tam giác ABC vuông tại A, đường cao AH, trên đó lấy điểm D. Trên tia đối của HA lấy E sao HE=AD. Đường thẳng vuông góc với AH tại D cắt AC tại F . chứng minh EB vuông góc EF
D. WRITING I. Choose the underlined part that needs correction33. She usually spend thirty minutes doing the shopping. A B C D34. Yesterday, they stayed at a childcare and help the disabled kids A B C D35. She enjoys to build doolhouses and posting pictures of them on social media. A B C DI. Write the second sentence so that it has the same mean...
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D. WRITING I. Choose the underlined part that needs correction
33. She usually spend thirty minutes doing the shopping.
A B C D
34. Yesterday, they stayed at a childcare and help the disabled kids
A B C D
35. She enjoys to build doolhouses and posting pictures of them on social media.
A B C D
I. Write the second sentence so that it has the same meaning to the first one.
36. They are interested in drinking tea after meals.
à They love ………………………………………………………….
37. You are hard-working, and your sister is hard-working, too.
à Both you and …………………………………………………………………
II. Write full sentences using the suggested words and phrases given :
38. She / like/ keep/ the bottles/ after/ drink/ the water.
39. Last summer/ we/ join/ community activities/ help / the elderly.
40. When/ I/ be/ a child/ I/ love/ play/ computer games.
33.C.doing
34.C.help
Vì trong một câu thường chỉ sử dung một thì
35.C.doolhouses
Vì viết sai
36.They love drinking tea after meals
37.Both you and your sister are hard-working
38.She likes keep the bottles after drink the water
39.Last summer we joined community activities help the elderly
40.When I was a child I loved playing computer games
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