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30 tháng 8

ĐKXĐ: \(\begin{cases}3x^2-7x+3\ge0\\ x^2-3x+4\ge0\\ x^2-2\ge0\\ 3x^2-5x-1\ge0\end{cases}\)

=>\(\left[\begin{array}{l}x\le-\sqrt2\\ x\ge\frac{5+\sqrt{37}}{6}\end{array}\right.\)

BPT =>\(\sqrt{3x^2 - 7x + 3} - \sqrt{3x^2 - 5x - 1} > \sqrt{x^2 - 2} - \sqrt{x^2 - 3x + 4}\)

=>\(\dfrac{(3x^2 - 7x + 3) - (3x^2 - 5x - 1)}{\sqrt{3x^2 - 7x + 3} + \sqrt{3x^2 - 5x - 1}} > \dfrac{(x^2 - 2) - (x^2 - 3x + 4)}{\sqrt{x^2 - 2} + \sqrt{x^2 - 3x + 4}}\)

=>\(\dfrac{-2x + 4}{\sqrt{3x^2 - 7x + 3} + \sqrt{3x^2 - 5x - 1}}>\dfrac{3x - 6}{\sqrt{x^2 - 2} + \sqrt{x^2 - 3x + 4}}\)

=>\(\dfrac{-2(x - 2)}{\sqrt{3x^2 - 7x + 3} + \sqrt{3x^2 - 5x - 1}}-\dfrac{3(x - 2)}{\sqrt{x^2 - 2} + \sqrt{x^2 - 3x + 4}}>0\)

=>\((x-2)\left[\dfrac{-2}{\sqrt{3x^2 - 7x + 3} + \sqrt{3x^2 - 5x - 1}}-\dfrac{3}{\sqrt{x^2 - 2} + \sqrt{x^2 - 3x + 4}}\right]>0\)

=>\((x - 2) \left[ \dfrac{2}{\sqrt{3x^2 - 7x + 3} + \sqrt{3x^2 - 5x - 1}} + \dfrac{3}{\sqrt{x^2 - 2} + \sqrt{x^2 - 3x + 4}} \right] < 0\)

=>x-2<0

=>x<2

Kết hợp ĐKXĐ, ta được: \(\left[\begin{array}{l}x\le-\sqrt2\\ \frac{5+\sqrt{37}}{6}\le x<2\end{array}\right.\)

Vậy: \(S = (-\infty, -\sqrt{2}] \cup \left[\dfrac{5+\sqrt{37}}{6}, 2\right)\)

27 tháng 12 2015

ai làm ơn làm phước tick cho mk lên 190 với

20 tháng 11 2017

(1)Phương trình đã cho tương đương với:
3x27x+33x25x1=x22x23x+43x2−7x+3−3x2−5x−1=x2−2−x2−3x+4
2x+43x27x+3+3x25x1=3x6<...

c: ĐKXĐ: \(x^3+3x^2+x-1\ge0\)

=>\(x^3+x^2+2x^2+2x-x-1\ge0\)

=>(x+1)\(\left(x^2+2x-1\right)\ge0\)

=>-1-\(\sqrt2\) <=x<=-1 hoặc \(x\ge-1+\sqrt2\)

\(x^2+5x+2=4\cdot\sqrt{x^3+3x^2+x-1}\)

=>\(x^2-x+6x-6=4\cdot\sqrt{x^3+3x^2+x-1}-8\)

=>(x-1)(x+6)=\(4\cdot\left(\sqrt{x^3+3x^2+x-1}-2\right)=4\cdot\frac{x^3+3x^2+x-1-4}{\sqrt{x^3+3x^2+x-1}+2}\)

=>(x-1)(x+6)=\(4\cdot\frac{x^3-x^2+4x^2-4x+5x-5}{\sqrt{x^3+3x^2+x-1}+2}\)

=>(x-1)(x+6)=4\(\frac{\left(x-1\right)\left(x^2+4x+5\right)}{\sqrt{x^3+3x^2+x-1}+2}\)

=>(x-1)\(\left\lbrack\frac{4\left(x^2+4x+5\right)}{\sqrt{x^3+3x^2+x-1}+2}-x-6\right\rbrack=0\)

=>x-1=0

=>x=1(nhận)

4 tháng 8 2017

\(\sqrt{3x^2-7x+3}-\sqrt{x^2-2}=\sqrt{3x^2-5x-1}-\sqrt{x^2-3x+4}\)

\(pt\Leftrightarrow\left(\sqrt{3x^2-7x+3}-1\right)-\left(\sqrt{x^2-2}-\sqrt{2}\right)=\left(\sqrt{3x^2-5x-1}-1\right)-\left(\sqrt{x^2-3x+4}-\sqrt{2}\right)\)

\(\Leftrightarrow\dfrac{3x^2-7x+3-1}{\sqrt{3x^2-7x+3}+1}-\dfrac{x^2-2-2}{\sqrt{x^2-2}+\sqrt{2}}=\dfrac{3x^2-5x-1-1}{\sqrt{3x^2-5x-1}+1}-\dfrac{x^2-3x+4-2}{\sqrt{x^2-3x+4}+\sqrt{2}}\)

\(\Leftrightarrow\dfrac{3x^2-7x+2}{\sqrt{3x^2-7x+3}+1}-\dfrac{x^2-4}{\sqrt{x^2-2}+\sqrt{2}}-\dfrac{3x^2-5x-2}{\sqrt{3x^2-5x-1}+1}+\dfrac{x^2-3x+2}{\sqrt{x^2-3x+4}+\sqrt{2}}=0\)

\(\Leftrightarrow\dfrac{\left(x-2\right)\left(3x-1\right)}{\sqrt{3x^2-7x+3}+1}-\dfrac{\left(x-2\right)\left(x+2\right)}{\sqrt{x^2-2}+\sqrt{2}}-\dfrac{\left(x-2\right)\left(3x+1\right)}{\sqrt{3x^2-5x-1}+1}+\dfrac{\left(x-1\right)\left(x-2\right)}{\sqrt{x^2-3x+4}+\sqrt{2}}=0\)

\(\Leftrightarrow\left(x-2\right)\left(\dfrac{3x-1}{\sqrt{3x^2-7x+3}+1}-\dfrac{x+2}{\sqrt{x^2-2}+\sqrt{2}}-\dfrac{3x+1}{\sqrt{3x^2-5x-1}+1}+\dfrac{x-1}{\sqrt{x^2-3x+4}+\sqrt{2}}\right)=0\)

Dễ thấy: \(\dfrac{3x-1}{\sqrt{3x^2-7x+3}+1}-\dfrac{x+2}{\sqrt{x^2-2}+\sqrt{2}}-\dfrac{3x+1}{\sqrt{3x^2-5x-1}+1}+\dfrac{x-1}{\sqrt{x^2-3x+4}+\sqrt{2}}< 0\)

\(\Rightarrow x-2=0\Rightarrow x=2\)

14 tháng 6

c:

ĐKXĐ: 6-5x>=0

=>5x<=6

=>x<=1,2

\(2\sqrt[3]{3x-2}-3\cdot\sqrt{6-5x}+16=0\)

=>\(2\cdot\sqrt[3]{3x-2}+4+12-3\cdot\sqrt{6-5x}=0\)

=>\(2\cdot\left(\sqrt[3]{3x-2}+2\right)+3\left(4-\sqrt{6-5x}\right)=0\)

=>\(2\cdot\frac{3x-2+8}{\sqrt[3]{\left(3x-2\right)^2}-2\cdot\sqrt[3]{3x-2}+4}+3\cdot\frac{16-6+5x}{4+\sqrt{6-5x}}=0\)

=>\(2\cdot\frac{3x+6}{\sqrt[3]{\left(3x-2\right)^2}-2\cdot\sqrt[3]{3x-2}+4}+3\cdot\frac{5x+10}{4+\sqrt{6-5x}}=0\)

=>\(\left(2\cdot\frac{3}{\sqrt[3]{\left(3x-2\right)^2}-2\cdot\sqrt[3]{3x-2}+4}+3\cdot\frac{5}{4+\sqrt{6-5x}}\right)\left(x+2\right)=0\)

=>x+2=0

=>x=-2(nhận)

d: ĐKXĐ: x>=1

\(\sqrt[3]{x+6}-2\cdot\sqrt{x-1}=4-x^2\)

=>\(\sqrt[3]{x+6}-2-2\cdot\sqrt{x-1}+2=4-x^2\)

=>\(\frac{x+6-8}{\sqrt[3]{\left(x+6\right)^2}+2\cdot\sqrt[3]{x+6}+4}+2\left(1-\sqrt{x-1}\right)=\left(2-x\right)\left(2+x\right)\)

=>\(\frac{x-2}{\sqrt[3]{\left(x+6\right)^2}+2\cdot\sqrt[3]{x+6}+4}+2\cdot\frac{1-x+1}{1+\sqrt{x-1}}=\left(2-x\right)\left(2+x\right)\)

=>\(\frac{x-2}{\sqrt[3]{\left(x+6\right)^2}+2\cdot\sqrt[3]{x+6}+4}-2\cdot\frac{x-2}{1+\sqrt{x-1}}-\left(2-x\right)\left(2+x\right)=0\)

=>\(\frac{x-2}{\sqrt[3]{\left(x+6\right)^2}+2\cdot\sqrt[3]{x+6}+4}-2\cdot\frac{x-2}{1+\sqrt{x-1}}+\left(x-2\right)\left(2+x\right)=0\)

=>\(\left(x-2\right)\left(\frac{1}{\sqrt[3]{\left(x+6\right)^2}+2\cdot\sqrt[3]{x+6}+4}-\frac{2}{1+\sqrt{x-1}}+\left(2+x\right)\right)=0\)

=>x-2=0

=>x=2(nhận)