giải nhanh giúp mình với ạ mình cảm ơn trước nhiều lắm
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18 tháng 2 2021
1) Vì x=25 thỏa mãn ĐKXĐ nên Thay x=25 vào biểu thức \(A=\dfrac{\sqrt{x}-2}{x+1}\), ta được:
\(A=\dfrac{\sqrt{25}-2}{25+1}=\dfrac{5-2}{25+1}=\dfrac{3}{26}\)
Vậy: Khi x=25 thì \(A=\dfrac{3}{26}\)
2) Ta có: \(B=\dfrac{\sqrt{x}-3}{\sqrt{x}+1}+\dfrac{2x+8\sqrt{x}-6}{x-\sqrt{x}-2}\)
\(=\dfrac{\left(\sqrt{x}-3\right)\left(\sqrt{x}-2\right)}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+1\right)}+\dfrac{2x+8\sqrt{x}-6}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+1\right)}\)
\(=\dfrac{x-5\sqrt{x}+6+2x+8\sqrt{x}-6}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+1\right)}\)
\(=\dfrac{3x+3\sqrt{x}}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+1\right)}\)
\(=\dfrac{3\sqrt{x}\left(\sqrt{x}+1\right)}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+1\right)}\)
\(=\dfrac{3\sqrt{x}}{\sqrt{x}-2}\)
TT
1
KY
9 tháng 9 2021
Refer
1. “Your cousin speaks English very well” Paul told me
Paul said that ___________my cousin spoke English very well____________
2. “The man broke out of prison yesterday” said the policeman
The policeman told us_that the man had broken out of prison the day beforr__
3. “I’ll lend you this book as soon as I finish it” Owen said to me
Owen said __me that he would lend me that book as soon as he finished it___
4. “I think I forgot to turn off the lights this morning” Brenda told Brian
Brenda told Brian ____that he thought he had forgotten to turn off the lights that morning.____
5. “I work eight hours a day, except when the children are on holiday” said Mrs. Wood
Mrs. Wood said me that he worked eight hours a day, excepted when the children were on holiday
6. “You’ve been making good progress this semester” Miss Lynn told me
Miss Lynn said that _____I had been making good progress that semester_________
7. “If you bought all the tickets, you would win the lottery” the man said
The man told me ______that If I had bought all the tickets, I would win the lottery______________
8. “I like swimming but I don’t go very often” Jill said to Pam
Jill said that ______he liked swimming but he didn’t go very often___________________________
9. “I want to buy it, but I haven’t brought any money” said Patrick
Patrick told me _________that he wanted to buy it, but he hadn’t brought any money_______________________
10. “I’m going to visit my aunt in Hue, but I’m not sure when” said Mai
Mai told me _________that she was going to visit her aunt in Hue, but she was not sure when__________________
N
1
21 tháng 6 2021
\(\Leftrightarrow2\left(x+1\right)^3=56\Leftrightarrow\left(x+1\right)^3=28\Leftrightarrow\)
HK
1
NU
1
12 tháng 3 2023
mở bài là giới thiệu về cụ nha mn em viết lộn ạ
thân bài là đóng góp ạ
22 tháng 9 2021
Đề ko rõ ràng \(\sqrt{x^2}+x+\dfrac{1}{4}\) hay \(\sqrt{x^2+x+\dfrac{1}{4}}\)??
NH
3
18 tháng 8 2021
a) ĐKXĐ: \(2x-3\ge0\Rightarrow x\ge\dfrac{3}{2}\)
b) ĐKXĐ: \(-\dfrac{2}{x}+5\ge0\Rightarrow x\ge\dfrac{2}{5}\)
c)ĐKXĐ: \(-3x-5>0\Rightarrow x>-\dfrac{5}{3}\)
d) ĐKXĐ: \(4x^2-4x+1\ge0\Rightarrow\left(2x-1\right)^2\ge0\) (luôn đúng)
28 tháng 6 2021
`a)25/(x+1)-1 1/6=-1/3-0,5`
`=>25/(x+1)=-1/3-1/2+1+1/6`
`=>25/(x+1)=1/3`
`=>75=x+1`
`=>x=74`
Vậy `x=74`
`b)(2x+25 3/5)^2-9/25=0`
`=>(2x+128/5)=9/25`
`**2x+128/5=3/5`
`=>2x=-125/5=-25`
`=>x=-25/2`
`**2x+128/5=-3/5`
`=>2x=-131/5`
`=>x=-131/10`
KA
1
TP
2 tháng 8 2021
d) Gọi x,y lần lượt là số mol Al, Fe
\(\left\{{}\begin{matrix}27x+56y=8,3\\1,5x+y=0,25\end{matrix}\right.\)
=> x=0,1 ; y=0,1
Kết tủa : Al(OH)3, Fe(OH)2
Bảo toàn nguyên tố Al: \(n_{Al\left(OH\right)_3}=n_{Al}=0,1\left(mol\right)\)
Bảo toàn nguyên tố Fe: \(n_{Fe\left(OH\right)_2}=n_{Fe}=0,1\left(mol\right)\)
=> \(m=0,1.78+0,1.90=16,8\left(g\right)\)
Nung kết tủa thu được chất rắn : Al2O3 và FeO
Bảo toàn nguyên tố Al: \(n_{Al_2O_3}.2=n_{Al}\Rightarrow n_{Al_2O_3}=0,05\left(mol\right)\)
Bảo toàn nguyên tố Fe: \(n_{FeO}=n_{Fe}=0,1\left(mol\right)\)
=> \(a=0,05.102+0,1.72=12,3\left(g\right)\)
Đăng tách ra đi bạn
Bài 5:
Theo đề, ta có:
\(\left(2x+5\right)^2-4x^2-12x=41\)
\(\Leftrightarrow20x-12x=41+25=66\)
hay \(x=8.25\left(m\right)\)
Chu vi là:
\(\left[\left(2\cdot8.25+5\right)^2+\left(4\cdot8.25^2+12\cdot8.25\right)\right]\cdot2=1667\left(m\right)\)