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29 tháng 4 2022

1.\(x=4-2\sqrt{3}-\left(\sqrt{3}\right)^2-2.\sqrt{3}.1+1^2=\left(\sqrt{3}-1\right)^2\)

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

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

\(B=A+1\)

\(\Leftrightarrow x-1=2\sqrt{x}+1+1\)

\(\Leftrightarrow x-1=2\sqrt{x}+2\)

\(\Leftrightarrow x-2x\sqrt{x}-3=0\)

\(\Leftrightarrow\left(\sqrt{x}-3\right)\left(\sqrt{x}+1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}\sqrt{x}=3\\\sqrt{x}=-1\left(vô.lý\right)\end{matrix}\right.\) \(\rightarrow x=\sqrt{3}\)

 

8 tháng 11 2021

1 D

2 B

3 F

4 C

5 A

6 E

8 tháng 11 2021

17.D

18.B

19.F

20.C

21.A

22.E

Đây bạn

30 tháng 9 2021

1 is watered by my father everymorning

2 is prepared by her mother in the kitchen

3 should be cleaned twice a day

4 repainting before Tet

5 was invited to his birthday party by John last night

6 of the car has to be repaired 

7 won't be hung in the living room

8 the most valuable painting in the national museum been stolen

9 were told this story by their grandmother when they visited her last week

10 taken by a man when we were......

11 given up smoking since last year

12 read War and Peace since 2005

C nguyên

=>2căn x+2+3 chia hết cho căn x+1

=>căn x+1 thuộc Ư(3)

=>căn x+1=1 hoặc căn x+1=3

=>x=4 hoặc x=0

31 tháng 5 2023

\(P=\dfrac{2\sqrt{x}+5}{\sqrt{x}+1}=\dfrac{2\sqrt{x}+2+3}{\sqrt{x}+1}=2+\dfrac{3}{\sqrt{x}+1}\)`(đk:x >=0)`

Để `P in ZZ`

`=> sqrt(x) +1 in Ư(3)={+-1;+-3}`

Mà `sqrt{x} +1 >0 AA x>=0`

`=> sqrt(x) +1 in {1;3}`

`@ sqrt{x} +1 =1 => x =0`

`@ sqrt(x) +1 =3 => x=4`

b: \(\Leftrightarrow\dfrac{-m^2+3}{m}=\dfrac{13}{4}\)

\(\Leftrightarrow-4m^2+12=13m\)

\(\Leftrightarrow4m^2-13m-12=0\)

\(\Leftrightarrow\left(m-4\right)\left(4m+3\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}m=4\\m=-\dfrac{3}{4}\end{matrix}\right.\)

2 tháng 11 2021

\(I=I1=I2=I3=\dfrac{U3}{R3}=\dfrac{7,5}{5}=1,5A\left(R1ntR2ntR3\right)\)

\(\left\{{}\begin{matrix}U=IR=1,5\left(4+3+5\right)=18V\\U1=I1.R1=1,5.4=6V\\U2=I2.R2=1,5.3=4,5V\end{matrix}\right.\)

a: \(E=x^4z^3y\left(\dfrac{2}{5}-0+1\right)=\dfrac{7}{5}x^4yz^3\)

b: \(E=\dfrac{7}{5}x^4yz^3=\dfrac{7}{5}\cdot2^4\cdot\dfrac{1}{2}\cdot\left(-1\right)^3=\dfrac{7}{5}\cdot8\cdot\left(-1\right)=-\dfrac{56}{5}\)

25 tháng 2 2022

a, \(=\left(\dfrac{2}{5}+1\right)x^4z^3y=\dfrac{7}{5}x^4z^3y\)

b, Thay x = 2 ; y = 1/2 ; z = -1 vào ta được 

\(\dfrac{7}{5}.16.\dfrac{-1}{2}.1=-\dfrac{56}{5}\)