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NV
Nguyễn Việt Lâm
Giáo viên
5 tháng 10 2021
a.
Đặt \(x+2y+1=a\)
\(\Rightarrow P=a^2+\left(a+4\right)^2=2a^2+8a+16=2\left(a+2\right)^2+8\ge8\)
\(P_{min}=8\) khi \(a=-2\) hay \(x+2y+3=0\)
b.
\(\sqrt{x}-1=a\ge0\Rightarrow\sqrt{x}=a+1\Rightarrow x=a^2+2a+1\)
\(Q=\dfrac{\left(a^2+2a+1\right)+\left(a+1\right)+1}{a}=\dfrac{a^2+3a+3}{a}=a+\dfrac{3}{a}+3\ge2\sqrt{\dfrac{3a}{a}}+3=3+2\sqrt{3}\)
\(Q_{min}=3+2\sqrt{3}\) khi \(a=\sqrt{3}\) hay \(x=4+2\sqrt{3}\)
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20 tháng 5 2021
30B 31B 32D 33D 34C 35B 36B 37C 38B 39A 40D 41D 42A 43D 44D 45A 46C 47B 48C 49B 50C 51C 52A 53D 54B 55C 56A 57C 58A 59D 60B
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DT
Đỗ Thanh Hải
CTVVIP
8 tháng 9 2021
1 have been
2 has worked
3 has lived
4 have just seen
5 has finished
6 hasn't done
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\(1,\\ a,=4-5y\\ b,=\dfrac{20x}{3y}\cdot\dfrac{6y}{4}=\dfrac{10x}{1}=10x\\ 2,\\ a,=\left(2x+2-4\right)\left(2x+2+4\right)=2\left(x+1-2\right)2\left(x+1+2\right)\\ =4\left(x-1\right)\left(x+3\right)\\ b,=\left(2xy-xz\right)+\left(6y-3z\right)\\ =2x\left(y-z\right)+3\left(y-z\right)=\left(2x+3\right)\left(y-z\right)\)