Giải phương trình: \(\sqrt{2x+3}+\sqrt{2x+\text{2}}=1\)
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\(\Leftrightarrow2x^2+2+2\sqrt{\left(x^2+x+1\right)\left(x^2-x+1\right)}=2x^2+4\)
\(\Leftrightarrow\sqrt{x^4+x^2+1}=1\)
\(\Leftrightarrow x^4+x^2=0\)
\(\Leftrightarrow x=0\)
`\sqrt{x^2+x+1}+\sqrt{x^2-x+1}=\sqrt{2x^2+4}`
`<=>2x^2+2+2\sqrt{x^4+x^2+1}=2x^2+3`
`<=>\sqrt{x^4+x^2+1}=1`
`<=>x^4+x^2=0`
`<=>x=0`
ĐK: \(x\ge\dfrac{1}{2}\)
\(pt\Leftrightarrow\sqrt{x}-1+\sqrt{2x-1}-1+x^2+x-2=0\)
\(\Leftrightarrow\dfrac{x-1}{\sqrt{x}+1}+\dfrac{2x-2}{\sqrt{2x-1}+1}+\left(x-1\right)\left(x+2\right)=0\)
\(\Leftrightarrow\left(\dfrac{1}{\sqrt{x}+1}+\dfrac{2}{\sqrt{2x-1}+1}+x+2\right)\left(x-1\right)=0\)
Vì \(\dfrac{1}{\sqrt{x}+1}+\dfrac{2}{\sqrt{2x-1}+1}+x+2>0\) nên \(x-1=0\Leftrightarrow x=1\left(tm\right)\)
a.
\(3\sqrt{-x^2+x+6}\ge2\left(1-2x\right)\)
\(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}-x^2+x+6\ge0\\1-2x< 0\end{matrix}\right.\\\left\{{}\begin{matrix}1-2x\ge0\\9\left(-x^2+x+6\right)\ge4\left(1-2x\right)^2\end{matrix}\right.\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}-2\le x\le3\\x>\dfrac{1}{2}\end{matrix}\right.\\\left\{{}\begin{matrix}x\le\dfrac{1}{2}\\25\left(x^2-x-2\right)\le0\end{matrix}\right.\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\dfrac{1}{2}< x\le3\\\left\{{}\begin{matrix}x\le\dfrac{1}{2}\\-1\le x\le2\end{matrix}\right.\end{matrix}\right.\)
\(\Rightarrow-1\le x\le3\)
b.
ĐKXĐ: \(x\ge0\)
\(\Leftrightarrow\sqrt{2x^2+8x+5}-4\sqrt{x}+\sqrt{2x^2-4x+5}-2\sqrt{x}=0\)
\(\Leftrightarrow\dfrac{2x^2+8x+5-16x}{\sqrt{2x^2+8x+5}+4\sqrt{x}}+\dfrac{2x^2-4x+5-4x}{\sqrt{2x^2-4x+5}+2\sqrt{x}}=0\)
\(\Leftrightarrow\dfrac{2x^2-8x+5}{\sqrt{2x^2+8x+5}+4\sqrt{x}}+\dfrac{2x^2-8x+5}{\sqrt{2x^2-4x+5}+2\sqrt{x}}=0\)
\(\Leftrightarrow\left(2x^2-8x+5\right)\left(\dfrac{1}{\sqrt{2x^2+8x+5}+4\sqrt{x}}+\dfrac{1}{\sqrt{2x^2-4x+5}+2\sqrt{x}}\right)=0\)
\(\Leftrightarrow2x^2-8x+5=0\)
\(\Leftrightarrow x=\dfrac{4\pm\sqrt{6}}{2}\)
ĐK: x≥-1
Ta có: \(\sqrt{2x+3}+\sqrt{2x+2}=1\)
\(\Leftrightarrow4x+5+2\sqrt{\left(2x+3\right)\left(2x+2\right)}=1\)
\(\Leftrightarrow\sqrt{4x^2+10x+6}=-2x-2\) ĐK:x≤1
\(\Leftrightarrow4x^2+10x+6=4x^2+8x+4\)
\(\Leftrightarrow2x=-2\Leftrightarrow x=-1\left(tm\right)\)