Mong mn giúp đỡ
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DT
Đỗ Thanh Hải
CTVVIP
14 tháng 6 2021
41 in
42 from
43 have
44 are
45 my
46 His
47 whenever
48 to
49 am
50 me
Mong mn giúp đỡ
NT
0
21 tháng 5 2021
\(f\left(x\right)=x^2-\left(2m-1\right)x-2\sqrt{x}+m^2-2m\)
1) đk: \(x\ge0\)
Thay m=2 vào \(f\left(x\right)=0\) ta được: \(x^2-3x-2\sqrt{x}=0\)
\(\Leftrightarrow\)\(\sqrt{x}\left(\sqrt{x}-2\right)\left(\sqrt{x}+1\right)^2=0\)
\(\Leftrightarrow\left[{}\begin{matrix}\sqrt{x}=0\\\sqrt{x}-2=0\\\sqrt{x}+1=0\left(vn\right)\end{matrix}\right.\)\(\Leftrightarrow\)\(\left[{}\begin{matrix}x=0\\x=4\end{matrix}\right.\)(tm)
2) Thay m=6 vào f(x) ta được:
\(f\left(x\right)=x^2-11x-2\sqrt{x}+24\)
\(f\left(x\right)\le0\) \(\Leftrightarrow x^2-11x-2\sqrt{x}+24\le0\) (bước này coi \(\sqrt{x}\) là nghiệm thì sẽ trở thành bpt
bậc 4 ,bấm máy tính sẽ tìm được nghiệm)
\(\Leftrightarrow\)\(\left(\sqrt{x}-3\right)\left(\sqrt{x}+2\right)\left(\sqrt{x}-\dfrac{-1+\sqrt{17}}{2}\right)\left(\sqrt{x}+\dfrac{1+\sqrt{17}}{2}\right)\le0\)
mà \(\sqrt{x}\ge0\) \(\Rightarrow\left\{{}\begin{matrix}\sqrt{x}+2>0\\\sqrt{x}+\dfrac{1+\sqrt{17}}{2}>0\end{matrix}\right.\)
bpt \(\Leftrightarrow\left(\sqrt{x}-3\right)\left(\sqrt{x}-\dfrac{-1+\sqrt{17}}{2}\right)\le0\)
\(\Leftrightarrow\sqrt{x}\in\left[\dfrac{-1+\sqrt{17}}{2};3\right]\)
\(\Leftrightarrow x\in\left[\dfrac{9-\sqrt{17}}{2};9\right]\)
AH
Akai Haruma
Giáo viên
29 tháng 4 2023
Lời giải:
a.
$A=\frac{3x+15}{(x-3)(x+3)}+\frac{x-3}{(x+3)(x-3)}-\frac{2(x+3)}{(x-3)(x+3)}$
$=\frac{3x+15+(x-3)-2(x+3)}{(x+3)(x-3)}=\frac{2x+6}{(x-3)(x+3)}$
$=\frac{2(x+3)}{(x-3)(x+3)}=\frac{2}{x-3}$
b.
Để $A=\frac{1}{2}$
$\Leftrightarrow \frac{2}{x-3}=\frac{1}{2}$
$\Leftrightarrow x-3=4$
$\Leftrightarrow x=7$ (tm)
MN
11
NT
0
3. Which flat is the .... most.... suitable for your family?
4. It's not easy....to find....a comfortable apartment here.
5. This building is ...bigger.... than that one.
6. The new flats are ....the most... comfortable of all.
Ex III:
1. Fruit is ...better than..... candy.
2. Cars are ....faster than.... bicycles.
3. Houses in the city are .....more expensive.... houses in the country.
4. Winter is ....colder than.... summer.
5. HCM City is ....bigger than.... Da Nang.
Ex I :
1. A 2. C
Ex II:
1. D
Ex III :
Ex IV:
1. What a bright room!
2. I have played soccer for 5 years.
3. My school is different from your school.
4. Nick's hobby is carving eggshells.
Homework:
Ex 1:
1. I .....read.... English every evening.
2. They have ....a lot of.... work to do.
3. Let's eat. I'm very ....hungry....
4. My watch is slow and my sister's is, ....too....
5. This is ....our.... new classmate.
6....What.... class are you in ?
7. Our house is near the school. We often go to school on ....foot...
Ex 2:
1. Mr.Lam ....grows...vegetables and ....raises...cattle.
2. This flat is more .....expensive....than that one.