các bn giúp mink với mink cần gấp
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Bài 4:
a: Ta có: \(-\left|x+1.1\right|\le0\forall x\)
\(\Leftrightarrow-\left|x+1.1\right|+1.5\le1.5\forall x\)
Dấu '=' xảy ra khi x=-1,1
b: Ta có: \(-4\left|x-2\right|\le0\forall x\)
\(\Leftrightarrow-4\left|x-2\right|+10\le10\forall x\)
Dấu '=' xảy ra khi x=2
Đk:\(-4\le x\le1.\)
Đặt \(\sqrt{1-x}=a,\sqrt{4+x}=b.\)
\(\Rightarrow\hept{\begin{cases}a+b=3\\a^2+b^2=5\end{cases}\Leftrightarrow\hept{\begin{cases}\left(a+b\right)^2=9\\a^2+b^2=5\end{cases}\Rightarrow}ab=2\Rightarrow\left(a-b\right)^2=1.\Rightarrow\orbr{\begin{cases}a-b=1\\a-b=-1\end{cases}\Rightarrow}\orbr{\begin{cases}a=2,b=1\\a=1,b=2\end{cases}}.}\)
Từ đó suy ra x=-3,x=0
các bạn ơi giúp mink bài 3 với nha mink cần gấp tối nay rồi !
giúp mink với nha mink cảm ơn nhìu lắm
Trả lời:
\(\left(x+1\right)+\left(x+2\right)+\left(x+3\right)+...+\left(x+9\right)+\left(x+10\right)=240\)
\(\Leftrightarrow\left(x+x+x+...+x+x\right)+\left(1+2+3+...+9+10\right)=240\)
\(\Leftrightarrow10x+\left(10+1\right)\times\left[\left(10-1\right)\div1+1\right]\div2=240\)
\(\Leftrightarrow10x+11\times10\div2=240\)
\(\Leftrightarrow10x+55=240\)
\(\Leftrightarrow10x=185\)
\(\Leftrightarrow x=18,5\)
Vậy \(x=18,5\)
Từ Hán-Việt là từ vựng sử dụng trong tiếng Việt có gốc từ tiếng Trung Quốc nhưng đọc theo âm Việt
(em lớp 6 nên ko chắc nah)
V,
41 . He last came here two months ago
=> He hasn't come here for two months
42. The last time I played tennis was in 1990
=> I haven't played tennis since 1990
43. It's three years since I saw Nam
=> I haven't seen Nam for three years
44. The last time I saw her was in 2006
=> I haven't seen her since 2006
45. He began to play tennis when he was 6
=> He has played tennis since he was 6
46. She bought that house in 1994
=> She has bought that house since 1994
47. She began to play piano 5 years ago
=> She has played piano for 5 years
48. Nam bought this bike last year
=> This bike has been bought by Nam last year
49. She was not seen three days ago
=> Nobody has seen her for three days
50. When did you last see Ann ?
=> How long have you seen Ann ?