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\(pt\Leftrightarrow2\left(x+1\right)\sqrt{x}+\sqrt{3\left(2x+1\right)\left(x+1\right)^2}=\left(x+1\right)\left(5x^2-8x+8\right)\)\(\Leftrightarrow2\left(x+1\right)\sqrt{x}+\left(x+1\right)\sqrt{3\left(2x+1\right)}-\left(x+1\right)\left(5x^2-8x+8\right)=0\)\(\Leftrightarrow\left(x+1\right)\left(2\sqrt{x}+\sqrt{3\left(2x+1\right)}-5x^2+8x-8\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=-1\\2\sqrt{x}+\sqrt{3\left(2x+1\right)}-5x^2-8+8x=0\circledast\end{matrix}\right.\)
Giải (*)\(2\sqrt{x}+\sqrt{3\left(2x+1\right)}-5x^2-8+8x=0\)
\(\Leftrightarrow2\sqrt{x}-2+\sqrt{3\left(2x+1\right)}-3=5x^2-8x+3\)
\(\Leftrightarrow\frac{4x-4}{2\sqrt{x}+2}+\frac{6x-6}{\sqrt{3\left(2x+1\right)}+3}=\left(x-1\right)\left(5x-3\right)\)
\(\Leftrightarrow\left(x-1\right)\left(\frac{2}{\sqrt{x}+1}+\frac{6}{\sqrt{3\left(2x+1\right)}+3}-5x+3\right)=0\)
x=1
bạn giải nốt cái còn lại nhá
\(\left(\sqrt{x+2}-\sqrt{x-1}\right)\left(\sqrt{2-x}+1\right)-1=0\) (ĐKXĐ : \(1\le x\le2\) )
\(\Leftrightarrow\sqrt{\left(2-x\right)\left(2+x\right)}+\sqrt{x+2}-\sqrt{\left(2-x\right)\left(x-1\right)}-\sqrt{x-1}-1=0\)
\(\Leftrightarrow\sqrt{\left(2-x\right)\left(2+x\right)}-\left(2-\sqrt{x+2}\right)-\sqrt{\left(2-x\right)\left(x-1\right)}+\left(1-\sqrt{x-1}\right)=0\)
\(\Leftrightarrow\sqrt{\left(2-x\right)\left(2+x\right)}-\frac{2-x}{\sqrt{x+2}+2}-\sqrt{\left(2-x\right)\left(x-1\right)}+\frac{2-x}{\sqrt{x-1}+1}=0\)
\(\Leftrightarrow\sqrt{2-x}\left(\sqrt{x+2}-\frac{\sqrt{2-x}}{\sqrt{x+2}+2}-\sqrt{x-1}+\frac{\sqrt{2-x}}{\sqrt{x-1}+1}\right)=0\)
\(\Leftrightarrow\left[\begin{array}{nghiempt}\sqrt{x-2}=0\\\sqrt{x+2}-\frac{\sqrt{2-x}}{\sqrt{x+2}+2}-\sqrt{x-1}+\frac{\sqrt{2-x}}{\sqrt{x-1}+1}=0\end{array}\right.\)
Với \(\sqrt{x-2}=0\) => x = 2 (TMĐK)
Với \(\sqrt{x+2}-\frac{\sqrt{2-x}}{\sqrt{x+2}+2}-\sqrt{x-1}+\frac{\sqrt{2-x}}{\sqrt{x-1}+1}=0\) , từ điều kiện \(1\le x\le2\) ta luôn có : \(\sqrt{x+2}-\frac{\sqrt{2-x}}{\sqrt{x+2}+2}-\sqrt{x-1}+\frac{\sqrt{2-x}}{\sqrt{x-1}+1}>0\)
Vậy phương trình có nghiệm : x = 2
\(\sqrt{4x^2+5x+1}-\sqrt{4x^2-4x+4}=9x-3\)(ĐKXĐ : \(x\le-1\)hoặc \(x\ge-\frac{1}{4}\))
\(\Leftrightarrow\left(\sqrt{4x^2+5x+1}-2\sqrt{7}x\right)-\left(\sqrt{4x^2-4x+4}-2\sqrt{7}x\right)-\left(9x-3\right)=0\)
\(\Leftrightarrow\frac{\left(4x^2+5x+1\right)-28x^2}{\sqrt{4x^2+5x+1}+2\sqrt{7}x}-\frac{\left(4x^2-4x+4\right)-28x^2}{\sqrt{4x^2-4x+4}+2\sqrt{7}x}-3\left(3x-1\right)=0\)
\(\Leftrightarrow\frac{-24x^2+5x+1}{\sqrt{4x^2+5x+1}+2\sqrt{7}x}+\frac{24x^2+4x-4}{\sqrt{4x^2-4x+4}+2\sqrt{7}x}-3\left(3x-1\right)=0\)
\(\Leftrightarrow\frac{-\left(3x-1\right)\left(8x+1\right)}{\sqrt{4x^2+5x+1}+2\sqrt{7}x}+\frac{4\left(3x-1\right)\left(2x+1\right)}{\sqrt{4x^2-4x+4}+2\sqrt{7}x}-3\left(3x-1\right)=0\)
\(\Leftrightarrow\left(3x-1\right)\left(\frac{8x+4}{\sqrt{4x^2-4x+4}+2\sqrt{7}x}-\frac{8x+1}{\sqrt{4x^2+5x+1}+2\sqrt{7}x}-3\right)=0\)
\(\Leftrightarrow\left[\begin{array}{nghiempt}3x-1=0\\\frac{8x+4}{\sqrt{4x^2-4x+4}+2\sqrt{7}x}-\frac{8x+1}{\sqrt{4x^2+5x+1}+2\sqrt{7}x}-3=0\end{array}\right.\)
Với 3x - 1 = 0 => x = \(\frac{1}{3}\) (TMĐK)
Với \(\frac{8x+4}{\sqrt{4x^2-4x+4}+2\sqrt{7}x}-\frac{8x+1}{\sqrt{4x^2+5x+1}+2\sqrt{7}x}-3=0\) , Từ điều kiện \(\left[\begin{array}{nghiempt}x\le-1\\x\ge-\frac{1}{4}\end{array}\right.\) ta luôn có : \(\frac{8x+4}{\sqrt{4x^2-4x+4}+2\sqrt{7}x}-\frac{8x+1}{\sqrt{4x^2+5x+1}+2\sqrt{7}x}-3>0\)
Vậy phương trình có nghiệm : \(x=\frac{1}{3}\)
1/ Đặt \(\sqrt[3]{x^2+5x-2}=t\Rightarrow x^2+5x=t^3+2\)
\(t^3+2=2t-2\)
\(\Leftrightarrow t^3-2t+4=0\)
\(\Leftrightarrow\left(t+2\right)\left(t^2-2t+2\right)=0\)
\(\Rightarrow t=-2\)
\(\Rightarrow\sqrt[3]{x^2+5x-2}=-2\)
\(\Leftrightarrow x^2+5x-2=-8\)
\(\Leftrightarrow x^2+5x+6=0\Rightarrow\left[{}\begin{matrix}x=-2\\x=-3\end{matrix}\right.\)
2/ \(\Leftrightarrow2x+11+3\sqrt[3]{\left(x+5\right)\left(x+6\right)}\left(\sqrt[3]{x+5}+\sqrt[3]{x+6}\right)=2x+11\)
\(\Leftrightarrow\sqrt[3]{\left(x+5\right)\left(x+6\right)}\left(\sqrt[3]{x+5}+\sqrt[3]{x+6}\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}\sqrt[3]{x+5}=0\\\sqrt[3]{x+6}=0\\\sqrt[3]{x+5}=-\sqrt[3]{x+6}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-5\\x=-6\\x+5=-x-6\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=-5\\x=-6\\x=-\frac{11}{2}\end{matrix}\right.\)
1/ \(3x^2+4x-3=4x\sqrt{4x-3}\)
\(\Leftrightarrow\left(4x^2-4x\sqrt{4x-3}+4x-3\right)-x^2=0\)
\(\Leftrightarrow\left(2x-\sqrt{4x-3}\right)^2-x^2=0\)
\(\Leftrightarrow\left(3x-\sqrt{4x-3}\right)\left(x-\sqrt{4x-3}\right)=0\)
\(\Leftrightarrow\left[\begin{matrix}3x=\sqrt{4x-3}\\x=\sqrt{4x-3}\end{matrix}\right.\)
\(\Leftrightarrow\left[\begin{matrix}9x^2-4x+3=0\\x^2-4x+3=0\end{matrix}\right.\)
\(\Leftrightarrow\left[\begin{matrix}x=1\\x=3\end{matrix}\right.\)
3.\(pt\Leftrightarrow\sqrt{3x+8}-\sqrt{3x+5}=\sqrt{5x-4}-\sqrt{5x-7}\)
\(\Leftrightarrow\frac{3x+8-5x+4}{\sqrt{3x+8}+\sqrt{5x+4}}-\frac{3x+5-5x+7}{\sqrt{3x+5}+\sqrt{5x+7}}=0\)
\(\Leftrightarrow\left(12-2x\right)\left(\frac{1}{\sqrt{3x+8}+\sqrt{5x+4}}+\frac{1}{\sqrt{3x+5}+\sqrt{5x+7}}\right)=0\)
\(\Rightarrow x=6\)
a/ ĐKXĐ: ...
Đặt \(\sqrt{x^2-2x-3}=a\ge0\Rightarrow x^2-2x=a^2+3\)
\(a^2+3+3a=7\)
\(\Leftrightarrow a^2+3a-4=0\Rightarrow\left[{}\begin{matrix}a=1\\a=-4\left(l\right)\end{matrix}\right.\)
\(\Rightarrow x^2-2x-3=1\Rightarrow x^2-2x-4=0\Rightarrow x=...\)
b/ \(\Leftrightarrow x^2-4x+6-\sqrt{x^2-4x+12}=0\)
\(\Leftrightarrow x^2-4x+12-\sqrt{x^2-4x+12}-6=0\)
Đặt \(\sqrt{x^2-4x+12}=a>0\)
\(a^2-a-6=0\Rightarrow\left[{}\begin{matrix}a=3\\a=-2\left(l\right)\end{matrix}\right.\)
\(\Rightarrow\sqrt{x^2-4x+12}=3\Rightarrow x^2-4x+3=0\Rightarrow...\)
c/ \(\Leftrightarrow x^2+11+\sqrt{x^2+11}-42=0\)
Đặt \(\sqrt{x^2+11}=a\)
\(a^2+a-42=0\Rightarrow\left[{}\begin{matrix}a=6\\a=-7\left(l\right)\end{matrix}\right.\)
\(\Rightarrow\sqrt{x^2+11}=6\Rightarrow x^2+11=36\Rightarrow...\)
d/ ĐKXĐ: ...
\(\Leftrightarrow x^2+2x-1+\sqrt{2x^2+4x+1}=0\)
Đặt \(\sqrt{2x^2+4x+1}=a\ge0\Rightarrow2x^2+4x=a^2-1\Rightarrow x^2+2x=\frac{a^2-1}{2}\)
\(\frac{a^2-1}{2}-1+a=0\)
\(\Leftrightarrow a^2+2a-3=0\Rightarrow\left[{}\begin{matrix}a=1\\a=-3\left(l\right)\end{matrix}\right.\)
\(\Rightarrow\sqrt{2x^2+4x+1}=1\Rightarrow2x^2+4x=0\Rightarrow...\)
e/
\(\Leftrightarrow x^2+5x+4-5\sqrt{x^2+5x+28}=0\)
Đặt \(\sqrt{x^2+5x+28}=a>0\Rightarrow x^2+5x=a^2-28\)
\(a^2-28+4-5a=0\)
\(\Leftrightarrow a^2-5a-24=0\Rightarrow\left[{}\begin{matrix}a=8\\a=-3\left(l\right)\end{matrix}\right.\)
\(\Rightarrow\sqrt{x^2+5x+28}=8\Rightarrow x^2+5x-36=0\Rightarrow...\)
P/s: tất cả các nghiệm sau khi giải ra x chắc chắn đều thỏa mãn
a) \(\sqrt{1+x}-\sqrt{8-x}+\sqrt{\left(1+x\right)\left(8-x\right)}=3\)
đặt t \(=\sqrt{1+x}-\sqrt{8-x}\)
\(\Leftrightarrow t^2=1+x-2\sqrt{\left(1+x\right)\left(8-x\right)}+8-x\)
\(\Leftrightarrow\sqrt{\left(1+x\right)\left(8-x\right)}=\dfrac{9-t^2}{2}\)
pt \(\Rightarrow t+\dfrac{9-t^2}{2}=3\)
\(\Leftrightarrow t^2-2t-3=0\)
\(\Leftrightarrow\left[{}\begin{matrix}t=-1\\t=3\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\sqrt{1+x}-\sqrt{8-x}=-1\\\sqrt{1+x}-\sqrt{8+x}=3\end{matrix}\right.\)
suy ra tìm đc x