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27 tháng 8

\(Q = \left( \frac{x+2}{x\sqrt{x} - \sqrt{x}} + \frac{\sqrt{x}}{x + \sqrt{x} + 1} - \frac{1}{1 - \sqrt{x}} \right) : \frac{\sqrt{x} - 1}{2}\)

Điều kiện: \(x\ge0\) , \(\) \(x\) khác \(1\)

Đổi dấu ở phân thức thứ 3: \(-\frac{1}{1 - \sqrt{x}} = +\frac{1}{\sqrt{x} - 1}\)

Phân tích mẫu thức thứ nhất thành nhân tử:

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

Mẫu thức chung trong ngoặc là: \(\sqrt{x}(\sqrt{x}-1)(x+\sqrt{x}+1)=\sqrt{x}(x\sqrt{x}-1)\)

Quy đồng và cộng các phân thức trong ngoặc:

\(\frac{x+2}{\sqrt{x}(\sqrt{x}-1)(\sqrt{x}+1)}\quad\)

\(A = \frac{x+2 + \sqrt{x}\cdot \sqrt{x}(\sqrt{x}-1) + \sqrt{x}(x+\sqrt{x}+1)}{\sqrt{x}(\sqrt{x}-1)(x+\sqrt{x}+1)}\)

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

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

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

Phân tích tử số thành nhân tử:

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

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

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

\(= (\sqrt{x} + 1)\left[2(x - \sqrt{x} + 1) + \sqrt{x}\right]\)

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

Thay vào biểu thức ta được:

\(Q = \frac{(\sqrt{x} + 1)(2x - \sqrt{x} + 2)}{\sqrt{x}(\sqrt{x}-1)(x+\sqrt{x}+1)} \cdot \frac{2}{\sqrt{x}-1}\)

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

\(\Leftrightarrow Q=\frac{2(\sqrt{x} + 1)(2x - \sqrt{x} + 2)}{\sqrt{x}(x\sqrt{x}-1)(\sqrt{x}-1)}\quad\) với \(x>0,\) \(x\) khác \(1\)


28 tháng 8

ĐKXĐ: x > 0 và x ≠ 1

$Q = \left( \frac{x+2}{x\sqrt{x}-\sqrt{x}} + \frac{\sqrt{x}}{x+\sqrt{x}+1} - \frac{1}{1-\sqrt{x}} \right) : \frac{\sqrt{x}-1}{2}$

$= \left( \frac{x+2}{\sqrt{x}(\sqrt{x}-1)(\sqrt{x}+1)} + \frac{\sqrt{x}}{x+\sqrt{x}+1} + \frac{1}{\sqrt{x}-1} \right) \cdot \frac{2}{\sqrt{x}-1}$

$= \left( \frac{x+2}{\sqrt{x}(\sqrt{x}-1)(x+\sqrt{x}+1)} + \frac{\sqrt{x}(\sqrt{x}-1)}{\sqrt{x}(\sqrt{x}-1)(x+\sqrt{x}+1)} + \frac{x+\sqrt{x}+1}{\sqrt{x}(\sqrt{x}-1)(x+\sqrt{x}+1)} \right) \cdot \frac{2}{\sqrt{x}-1}$

$= \frac{x + 2 + x - \sqrt{x} + x + \sqrt{x} + 1}{\sqrt{x}(\sqrt{x}-1)(x+\sqrt{x}+1)} \cdot \frac{2}{\sqrt{x}-1}$

$= \frac{3x + 3}{\sqrt{x}(\sqrt{x}-1)(x+\sqrt{x}+1)} \cdot \frac{2}{\sqrt{x}-1}$

$= \frac{6(x+1)}{\sqrt{x}(\sqrt{x}-1)^2(x+\sqrt{x}+1)}$

8 tháng 9 2021

\(e,\left(5+2\sqrt{6}\right)\left(49-20\sqrt{6}\right)\sqrt{5-2\sqrt{6}}\\ =\left(5+2\sqrt{6}\right)\left(\sqrt{3}-\sqrt{2}\right)\left(5-2\sqrt{6}\right)^2\\ =\left(5-2\sqrt{6}\right)\left(\sqrt{3}-\sqrt{2}\right)\\ =\left(\sqrt{3}-\sqrt{2}\right)^2\left(\sqrt{3}-\sqrt{2}\right)=\left(\sqrt{3}-\sqrt{2}\right)^3\)

\(f,\left(2\sqrt{6}-4\sqrt{3}+5\sqrt{2}-\dfrac{1}{4}\sqrt{8}\right)\cdot3\sqrt{6}\\ =36-36\sqrt{2}+30\sqrt{3}-3\sqrt{3}=36-36\sqrt{2}+27\sqrt{3}\)

\(g,\left(2+\sqrt{3}-\sqrt{2}\right)\left(2-\sqrt{3}-\sqrt{2}\right)\left(3+\sqrt{2}\right)\sqrt{3-2\sqrt{2}}\\ =\left[\left(2-\sqrt{2}\right)^2-\left(\sqrt{3}\right)^2\right]\left(3+\sqrt{2}\right)\sqrt{\left(\sqrt{2}-1\right)^2}\\ =\left(3-4\sqrt{2}\right)\left(3+\sqrt{2}\right)\left(\sqrt{2}-1\right)\\ =\left(1-9\sqrt{2}\right)\left(\sqrt{2}-1\right)\\ =10\sqrt{2}-37\)

\(h,A=\sqrt{4+\sqrt{10+2\sqrt{5}}}+\sqrt{4-\sqrt{10+2\sqrt{5}}}\\ A^2=4+\sqrt{10+2\sqrt{5}}+4-\sqrt{10+2\sqrt{5}}+2\sqrt{\left(4+\sqrt{10+2\sqrt{5}}\right)\left(4-\sqrt{10+2\sqrt{5}}\right)}\\ A^2=8+2\sqrt{6-2\sqrt{5}}\\ A^2=8+2\left(\sqrt{5}-1\right)\\ A^2=6+2\sqrt{5}\\ A=\sqrt{6+2\sqrt{5}}=\sqrt{\left(\sqrt{5}+1\right)^2}=\sqrt{5}+1\)

8 tháng 9 2021

\(b,\sqrt{15-\sqrt{216}}+\sqrt{33-12\sqrt{6}}\\ =\sqrt{15-6\sqrt{6}}+\sqrt{\left(2\sqrt{6}-3\right)^2}\\ =\sqrt{\left(3-\sqrt{6}\right)^2}+2\sqrt{6}-3\\ =3-\sqrt{6}+2\sqrt{6}-3=\sqrt{6}\)

\(c,\sqrt{2-\sqrt{3}}\left(\sqrt{6}+\sqrt{2}\right)\\ =\sqrt{12-6\sqrt{3}}+\sqrt{4-2\sqrt{3}}\\ =\sqrt{\left(3-\sqrt{3}\right)^2}+\sqrt{\left(\sqrt{3}-1\right)^2}\\ =3-\sqrt{3}+\sqrt{3}-1=2\)

8 tháng 9 2021

c: \(\sqrt{2-\sqrt{3}}\cdot\left(\sqrt{6}+\sqrt{2}\right)\)

\(=\sqrt{4-2\sqrt{3}}\cdot\left(\sqrt{3}+1\right)\)

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

=3-1

=2

2 tháng 3 2022

ĐKXĐ: \(x>2\)

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

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

- Với \(x\ge6\Rightarrow A=\dfrac{\sqrt{x-2}-2+\sqrt{x-2}+2}{\dfrac{x-2}{x}}=\dfrac{2x\sqrt{x-2}}{x-2}=\dfrac{2x}{\sqrt{x-2}}\)

- Với \(2< x< 6\Rightarrow A=\dfrac{2-\sqrt{x-2}+\sqrt{x-2}+2}{\dfrac{x-2}{x}}=\dfrac{4x}{x-2}\)

3 tháng 3 2022

em cảm ơn ạ

 

19 tháng 7 2021

a) Ta có: \(B=\sqrt{16x+16}-\sqrt{9x+9}+\sqrt{4x+4}+\sqrt{x+1}\)

\(=4\sqrt{x+1}-3\sqrt{x+1}+2\sqrt{x+1}+\sqrt{x+1}\)

\(=4\sqrt{x+1}\)

b) Để B=16 thì \(4\sqrt{x+1}=16\)

\(\Leftrightarrow x+1=16\)

hay x=15

19 tháng 7 2021

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9 tháng 9 2021

\(C=\left(\dfrac{3}{x-1}+\dfrac{1}{\sqrt{x}+1}\right):\dfrac{1}{\sqrt{x}+1}\)

\(=\dfrac{3+\sqrt{x}-1}{\left(\sqrt{x}+1\right)\left(\sqrt{x}-1\right)}\cdot\dfrac{\sqrt{x}+1}{1}\)

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

27 tháng 9 2015

2P = 24.(5^2 + 1 )( 5^4 + 1 ) (5^8 +  1 )(5^16 + 1 )

2P = ( 5^2 - 1 )((5^2  + 1 )( 5^4 + 1 ) (5^ 8 + 1 )( 5^ 16 + 1)

2P = ( 5 ^ 4 - 1 )( 5 ^ 4 + 1 ) (5^8 + 1 )(5^16 + 1 )

2P = ( 5 ^8 - 1 )( 5^8 + 1 )( 5^16 + 1)

2P = ( 5 ^16 - 1 )( 5^16 + 1 )

2P = 5^32 - 1 

=> P = \(\frac{5^{32}-1}{2}\)

23 tháng 9 2021

\(ĐK:x\ge0;x\ne4\\ P=\dfrac{5x+10\sqrt{x}-\left(3-\sqrt{x}\right)\left(\sqrt{x}-2\right)-6x}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}\\ P=\dfrac{5x+10\sqrt{x}-5\sqrt{x}+6+x-6x}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}\\ P=\dfrac{5\sqrt{x}+6}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}\)

23 tháng 9 2021

\(P=\dfrac{5\sqrt{x}}{\sqrt{x}-2}-\dfrac{3-\sqrt{x}}{\sqrt{x}+2}+\dfrac{6x}{4-x}\left(đk:x\ge0,x\ne4\right)\)

\(=\dfrac{5\sqrt{x}\left(\sqrt{x}+2\right)-\left(3-\sqrt{x}\right)\left(\sqrt{x}-2\right)-6x}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}\)

\(=\dfrac{5x+10\sqrt{x}+x-5\sqrt{x}+6-6x}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}=\dfrac{5\sqrt{x}+6}{x-4}\)

12 tháng 9 2021

Ta có: \(\dfrac{\sqrt{15}-\sqrt{5}}{\sqrt{3}-1}+\sqrt{\left(2-\sqrt{5}\right)^2}-2\sqrt{5}\)

\(=\sqrt{5}+\sqrt{5}-2-2\sqrt{5}\)

=-2

23 tháng 9 2021

\(ĐK:x>0;x\ne4\\ B=\dfrac{\sqrt{x}+2}{\sqrt{x}}\cdot\dfrac{x}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}+\dfrac{1}{\sqrt{x}-2}+\dfrac{1}{\sqrt{x}+2}\\ B=\dfrac{\sqrt{x}}{\sqrt{x}-2}+\dfrac{1}{\sqrt{x}-2}+\dfrac{1}{\sqrt{x}+2}\\ B=\dfrac{x+2\sqrt{x}+\sqrt{x}+2+\sqrt{x}-2}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}\\ B=\dfrac{x+4\sqrt{x}}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}=\dfrac{\sqrt{x}\left(\sqrt{x}+4\right)}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}\)

23 tháng 9 2021

Ta có: \(B=\dfrac{\sqrt{x}+2}{\sqrt{x}}\cdot\dfrac{x}{x-4}+\dfrac{1}{\sqrt{x}-2}+\dfrac{1}{\sqrt{x}+2}\)

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

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

\(=\dfrac{x+4\sqrt{x}}{x-4}\)

6 tháng 6 2017

ok mk sẽ giải

7 tháng 6 2017

Gọi \(A=\sqrt{2+\sqrt{3}}-\sqrt{2-\sqrt{3}}\)

\(\Leftrightarrow\sqrt{2}A=\sqrt{2}.\sqrt{2+\sqrt{3}}-\sqrt{2}.\sqrt{2-\sqrt{3}}\)

\(=\sqrt{4+2.\sqrt{3}}-\sqrt{4-2.\sqrt{3}}\)

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

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

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

\(\Rightarrow A=\frac{2}{\sqrt{2}}=\sqrt{2}\)