\(\sqrt{x^2-2x+4}+\sqrt{x^2+5}=9-2x\left(đk:x\le\dfrac{9}{2}\right)\)

\(\Leftrightarrow x^2-2x+4+x^2+5+2\sqrt{\left(x^2-2x+4\right)\left(x^2+5\right)}=81-36x+4x^2\)

\(\Leftrightarrow2\sqrt{\left(x^2-2x+4\right)\left(x^2+5\right)}=2x^2-34x+72\)

\(\Leftrightarrow4\left(x^2-2x+4\right)\left(x^2+5\right)=4x^4+1156x^2+5184-136x^3+288x^2-4896x\)

\(\Leftrightarrow4x^4-8x^3+36x^2-40x+80=4x^4-136x^3+1444x^2-4896x+5184\)

\(\Leftrightarrow128x^3-1408x^2+4856x-5104=0\)

\(\Leftrightarrow128x^2\left(x-2\right)-1152x\left(x-2\right)+2552\left(x-2\right)=0\)

\(\Leftrightarrow\left(x-2\right)\left(128x^2-1152x+2552\right)=0\)

\(\Leftrightarrow x=2\left(tm\right)\)(do \(128x^2-1152x+2552>0\))

câu 6 thể tích 1kg khí ở 0 độ 1,29 m³ 

áp dụng đẳng quá trình \(\dfrac{P_0V_0}{T_0}=\dfrac{PV}{T}\Leftrightarrow\dfrac{1,01.10^5.1,29}{0+273}=\dfrac{3.10^5.V}{70+273}\Rightarrow V\approx0,5456\left(m^3\right)\)

khối lượng riêng 0,5456kg/m³

ĐKXĐ: \(x\ne y,x\ne-y\)

\(hpt\Leftrightarrow\left(\dfrac{1}{x+y}+\dfrac{1}{x-y}\right)-\left(\dfrac{1}{x+y}+\dfrac{1}{x-y}\right)=\dfrac{5}{8}-\dfrac{3}{8}\)

\(\Leftrightarrow0=\dfrac{1}{4}\left(VLý\right)\)

Vậy hpt vô nghiệm

má bài này lol thắng cx đăng tr :vv

\(a=\dfrac{1}{x};b=\dfrac{1}{y};c=\dfrac{1}{z}\Rightarrow\left\{{}\begin{matrix}a+b+c=2\\2ab-c^2=4\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}c=2-a-b\\2ab-\left(2-a-b\right)^2=4\end{matrix}\right.\Leftrightarrow}}\left\{{}\begin{matrix}c=2-a-b\\2ab-4-a^2-b^2+4a+4a-2ab-4=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}c=2-a-b\\\left(a-2\right)^2+\left(b-2\right)^2=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}a=2\\b=2\\c=-2\end{matrix}\right.\Rightarrow}\left\{{}\begin{matrix}x=\dfrac{1}{2}\\y=\dfrac{1}{2}\\z=-\dfrac{1}{2}\end{matrix}\right.\)

a:

C1: =3/4*2*1/2=3/2*1/2=3/4

C2: =1/2*2*3/4=1*3/4=3/4

b: 

C1: =5/4*5/7=25/28

C2: =3/4*5/7+1/2*5/7=15/28+5/14=25/28

c: 

C1: =13/21(5/7+2/7)=13/21

C2: =65/147+26/147=91/147=13/21

1 It was such a difficult climb that we stopped to rest several times

2 She didn't ran fast enough to win the race

3 It was such a heavy bag that I had to ask for help

4 The house is too small for us to live in

5 Jack's suit was so elegant that everyone complimented him

6 My sister is not old enough to watch horror films

7 My mother is such a wise person that people often aske her for advice

8 The package is not light enough for you to lift by yourself

9 This book is too old for the children to eat

10 It was such an interesting book that I couldn't put it down

11 It is such a weak bird that it can't fly

12 These boyss aren't old enough to watch that film

13 They are such small sandals that they don't fit me

em chịu_{em thua}

cái gì đây?

của bạn nè.Mik lớp 5 nhưng vẫn phải học thuộc hết 

\(Q=x-2-2\sqrt{x-2}+4\)

\(=\left(\sqrt{x-2}-1\right)^2+3>=3\)

Dấu = xảy ra khi x=3

\(Q=x+2-2\sqrt{x-2} \)

\(Q=x-2-2\sqrt{x-2}+4 \)

\(Q=(\sqrt{x-2}-1)^2+3\)

Vì \((\sqrt{x-2}-1)^2\)\(\ge\)\(0\)

\(\Leftrightarrow\)\((\sqrt{x-2}-1)^2+3\)\(\ge3\)

Vậy GTNN Q=3