1. He is used to------------ up early in the morning.
A. get B. getting C. have gotten D. got
2. The boy was kept indoors----------- naughty.
A. to be B. have been C. for being D. when he
3. I shall never forget-----------with you to Paris last year.
A. staying B. to staying C. to stay D. stayed
4. I am looking forward to -----------you.
A. having seen B. seeing C. to see D. all are wrong
5. I am always remember------------ off the lights before I leave my house.
A. turning B. to turn C. turned D. being turned
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1, \(=\left[\frac{\left(1-x\right)\left(1+x+x^2\right)}{1-x}-x\right]:\frac{1-x^2}{\left(1-x\right)-x^2\left(1-x\right)}\)
\(=\left(1+x+x^2-x\right):\frac{1-x^2}{\left(1-x\right)\left(1-x^2\right)}\)\(=\left(x^2+1\right)\left(1-x\right)\)
2, để B<0 <=> (x2+1)(1-x)<0
vì x^2+1 > 0 với mọi x
=> \(\hept{\begin{cases}x^2+1>0\\1-x< 0\end{cases}\Leftrightarrow x>1}\)
3, \(\left|x-4\right|=5\Leftrightarrow\orbr{\begin{cases}x=9\\x=-1\left(loại\right)\end{cases}}\)
Thay x=9 vào B ta có: B=(92+1)(1-9)=82.(-8)=-656
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VT \(\ge\frac{\sqrt{3\sqrt[3]{x^3.y^3.1}}}{xy}+\frac{\sqrt{3\sqrt[3]{y^3.z^3.1}}}{yz}+\frac{\sqrt{3\sqrt[3]{z^3.x^3.1}}}{zx}\)( cauchy)
= \(\sqrt{\frac{3}{xy}}+\sqrt{\frac{3}{yz}}+\sqrt{\frac{3}{zx}}\)
\(\ge3\sqrt{3}\)( cauchy)
"=" <=> x = y =z.
Bài này dùng \(a^3+b^3\ge ab\left(a+b\right)\) được không nhỉ ??
Em ngại làm lắm cô Chi, cô thử cách này có được không ạ ?
\(xyz+x^3+y^3\ge xy\left(x+y+z\right)\)\(\Rightarrow\sqrt{1+x^3+y^3}\ge\sqrt{xy\left(x+y+z\right)}\)
Các mấy cái kia cũng biến đổi vậy.
Không chắc nx :((
1. He is used to------------ up early in the morning.
A. get B. getting C. have gotten D. got
2. The boy was kept indoors----------- naughty.
A. to be B. have been C. for being D. when he
3. I shall never forget-----------with you to Paris last year.
A. staying B. to staying C. to stay D. stayed
4. I am looking forward to -----------you.
A. having seen B. seeing C. to see D. all are wrong
5. I am always remember------------ off the lights before I leave my house.
A. turning B. to turn C. turned D. being turned