giúp em bài 8 bài 9 với ạ
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giúp em bài 8 với 9 ạ :<
25 tháng 10 2021
Bài 8:
a) \(A=\dfrac{\sqrt{a}-1}{\sqrt{a}}.\dfrac{\sqrt{a}+1+\sqrt{a}-1}{\left(\sqrt{a}-1\right)\left(\sqrt{a}+1\right)}=\dfrac{2\sqrt{a}}{\sqrt{a}\left(\sqrt{a}+1\right)}=\dfrac{2}{\sqrt{a}+1}\)
b) \(A=\dfrac{2}{\sqrt{a}+1}=\dfrac{2}{\sqrt{3-2\sqrt{2}}+1}=\dfrac{2}{\sqrt{\left(\sqrt{2}-1\right)^2}+1}=\dfrac{2}{\sqrt{2}-1+1}=\dfrac{2}{\sqrt{2}}=\sqrt{2}\)
Bài 9:
\(pt\Leftrightarrow\sqrt{\left(3x+1\right)^2}=2\)\(\Leftrightarrow\left|3x+1\right|=2\)
\(\Leftrightarrow\left[{}\begin{matrix}3x+1=2\\3x+1=-2\end{matrix}\right.\)\(\Leftrightarrow\left[{}\begin{matrix}3x=1\\3x=-3\end{matrix}\right.\)\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{3}\\x=-1\end{matrix}\right.\)
Giải giúp em bài 8 9 10 đi ạ
25 tháng 6 2021
Câu 15:
1: Ta có: \(\dfrac{1}{1-\sqrt{2}}-\dfrac{1}{1+\sqrt{2}}\)
\(=\dfrac{1+\sqrt{2}-1+\sqrt{2}}{\left(1-\sqrt{2}\right)\left(1+\sqrt{2}\right)}\)
\(=-2\sqrt{2}\)
2: Ta có: \(\dfrac{1}{\sqrt{5}+1}+\dfrac{1}{\sqrt{5}-1}\)
\(=\dfrac{\sqrt{5}-1+\sqrt{5}+1}{\left(\sqrt{5}+1\right)\left(\sqrt{5}-1\right)}\)
\(=\dfrac{2\sqrt{5}}{4}=\dfrac{\sqrt{5}}{2}\)
HJ
1
2 tháng 10 2021
Bài 10:
a: \(\overrightarrow{AB}+\overrightarrow{BO}+\overrightarrow{OA}\)
\(=\overrightarrow{AO}+\overrightarrow{OA}=\overrightarrow{0}\)
b: \(\overrightarrow{OA}+\overrightarrow{BC}+\overrightarrow{DO}+\overrightarrow{CD}\)
\(=\overrightarrow{OA}+\overrightarrow{DO}+\overrightarrow{BD}\)
\(=\overrightarrow{OA}+\overrightarrow{BO}=\overrightarrow{BA}\)
TN
1
26 tháng 10 2021
b: \(BC=\sqrt{89}\left(cm\right)\)
\(\sin\widehat{B}=\dfrac{5\sqrt{89}}{89}\)
\(\Leftrightarrow\widehat{B}\simeq32^0\)
\(\widehat{C}=58^0\)
NV
Nguyễn Việt Lâm
Giáo viên
19 tháng 3 2022
8a.
\(\lim\limits_{x\rightarrow1^+}f\left(x\right)=\lim\limits_{x\rightarrow1^+}\left(3x^2-5x+1\right)=3-5+1=-1\)
\(\lim\limits_{x\rightarrow1^-}f\left(x\right)=\lim\limits_{x\rightarrow1^-}\left(-3x+2\right)=-3+2=-1\)
\(\Rightarrow\lim\limits_{x\rightarrow1^+}f\left(x\right)=\lim\limits_{x\rightarrow1^-}f\left(x\right)\Rightarrow\) hàm có giới hạn tại \(x=1\)
Đồng thời \(\lim\limits_{x\rightarrow1}f\left(x\right)=-1\)
b.
\(\lim\limits_{x\rightarrow2^+}f\left(x\right)=\lim\limits_{x\rightarrow2^+}\dfrac{x^3-8}{x-2}=\lim\limits_{x\rightarrow2^+}\dfrac{\left(x-2\right)\left(x^2+2x+4\right)}{x-2}\)
\(=\lim\limits_{x\rightarrow2^+}\left(x^2+2x+4\right)=12\)
\(\lim\limits_{x\rightarrow2^-}f\left(x\right)=\lim\limits_{x\rightarrow2^-}\left(2x+1\right)=5\)
\(\Rightarrow\lim\limits_{x\rightarrow2^+}f\left(x\right)\ne\lim\limits_{x\rightarrow2^-}f\left(x\right)\Rightarrow\) hàm ko có giới hạn tại x=2
NV
Nguyễn Việt Lâm
Giáo viên
19 tháng 3 2022
9.
\(\lim\limits_{x\rightarrow0^+}f\left(x\right)=\lim\limits_{x\rightarrow0^+}\dfrac{x^2+mx+2m+1}{x+1}=\dfrac{0+0+2m+1}{0+1}=2m+1\)
\(\lim\limits_{x\rightarrow0^-}f\left(x\right)=\lim\limits_{x\rightarrow0^-}\dfrac{2x+3m-1}{\sqrt{1-x}+2}=\dfrac{0+3m-1}{1+2}=\dfrac{3m-1}{3}\)
Hàm có giới hạn khi \(x\rightarrow0\) khi:
\(\lim\limits_{x\rightarrow0^+}f\left(x\right)=\lim\limits_{x\rightarrow0^-}f\left(x\right)\Rightarrow2m+1=\dfrac{3m-1}{3}\)
\(\Rightarrow m=-\dfrac{4}{3}\)
KY
24 tháng 7 2021
refer
1. like/dinner/house/would/have/tonight/you/to/my/at/?
Would you like to have dinner at my house tonight?
2.detective/parents/going/movie/this afternoon/we/see/with/are/a/our/to/.
We are going to see a detective movies with our parents this afternoon.
3.watching/prefers/to/brother/books/TV/my/reading.
My brother prefers watching TV and reading to books.
4.daughter / best/kinds/does /like/what/TV program/your /of/?
What kind of program does your daughter like best?
5. showing/local cinema/is/horror film / the/a/there/next week/at.
There is horror film showing at that local cinema next week.
6.durians /and/my/ like/much/does/I/very/father/so
I like durians very much so does my father.
7.went/she/stomachache/the doctor's/ an/Lan/because/awful to/ had.
Lan's went to the doctor's because she had an awful stomache.
8.have/the/farm/often/them/vegatables/from/dirt/on.
Vegetables from the farm of ten have dirt on time.
9.in/work/will/do/all/ the/machines/for/the/future/us.
In the future, machines will do all the work for us.
10.it/hours/about/two/Hoa Binh/to takes /by /get/to/couch.
It 's take us about to hours to get to Hoa Binh by couch.
DT
Đỗ Thanh Hải
CTVVIP
24 tháng 7 2021
1 Would you like to have dinner at my house tonight?
2 We are going to see a detective movie with our parents this afternoon
3 My brother prefers watching TV to reading books
4 What kinds of TV program does your daughter like best?
5 There is a horror film showing at the local cinema next week
7 I like durians very much and so does my father
8 Vegetables often have dirt from the farm on them
9 Machines will do all the work for us in the future
10 It's takes about 2 hours to get to HoaBinh by coach
Bài 8:
a: Ta có: \(M=\dfrac{2\sqrt{x}-9}{x-5\sqrt{x}+6}-\dfrac{\sqrt{x}+3}{\sqrt{x}-2}+\dfrac{2\sqrt{x}+1}{\sqrt{x}-3}\)
\(=\dfrac{2\sqrt{x}-9-x+9+2x-4\sqrt{x}+\sqrt{x}-2}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-3\right)}\)
\(=\dfrac{\sqrt{x}+1}{\sqrt{x}-3}\)
b: Thay \(x=11-6\sqrt{2}\) vào M, ta được:
\(M=\dfrac{3-\sqrt{2}+1}{3-\sqrt{2}-3}=\dfrac{4-\sqrt{2}}{-\sqrt{2}}=-2\sqrt{2}+1\)
Bài 8:
a) \(M=\dfrac{2\sqrt{x}-9-\left(\sqrt{x}+3\right)\left(\sqrt{x}-3\right)+\left(2\sqrt{x}+1\right)\left(\sqrt{x}-2\right)}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-3\right)}\)
\(=\dfrac{2\sqrt{x}-9-x+9+2x-3\sqrt{x}-2}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-3\right)}=\dfrac{x-\sqrt{x}-2}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-3\right)}=\dfrac{\left(\sqrt{x}-2\right)\left(\sqrt{x}+1\right)}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-3\right)}=\dfrac{\sqrt{x}+1}{\sqrt{x}-3}\)
b) \(M=\dfrac{\sqrt{x}+1}{\sqrt{x}-3}=\dfrac{\sqrt{11-6\sqrt{2}}+1}{\sqrt{11-6\sqrt{2}}-3}=\dfrac{\sqrt{\left(3-\sqrt{2}\right)^2}+1}{\sqrt{\left(3-\sqrt{2}\right)^2}-3}=\dfrac{4-\sqrt{2}}{-\sqrt{2}}=1-2\sqrt{2}\)
c) \(M=\dfrac{\sqrt{x}+1}{\sqrt{x}-3}=3\)
\(\Leftrightarrow3\sqrt{x}-9=\sqrt{x}+1\Leftrightarrow2\sqrt{x}=10\Leftrightarrow\sqrt{x}=5\Leftrightarrow x=25\left(tm\right)\)
d) \(M=\dfrac{\sqrt{x}+1}{\sqrt{x}-3}< 1\)
\(\Leftrightarrow\sqrt{x}+1< \sqrt{x}-3\Leftrightarrow1< -3\left(VLý\right)\)
Vậy \(S=\varnothing\)
e) \(M=\dfrac{\sqrt{x}+1}{\sqrt{x}-3}=1+\dfrac{4}{\sqrt{x}-3}\in Z\)
\(\Rightarrow\sqrt{x}-3\inƯ\left(4\right)=\left\{-4;-2;-1;1;2;4\right\}\)
Kết hợp đk:
\(\Rightarrow x\in\left\{1;16;25;49\right\}\)