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b.
ĐKXĐ: \(x\ge-1\)
\(\sqrt{\left(x+1\right)\left(x+35\right)}-14\sqrt{x+35}+84-6\sqrt{x+1}=0\)
\(\Leftrightarrow\sqrt{x+1}\left(\sqrt{x+35}-14\right)-6\left(\sqrt{x+35}-14\right)=0\)
\(\Leftrightarrow\left(\sqrt{x+1}-6\right)\left(\sqrt{x+35}-14\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}\sqrt{x+1}=6\\\sqrt{x+35}=14\end{matrix}\right.\)
\(\Leftrightarrow...\)
a. ĐKXĐ: \(-1\le x\le1\)
Đặt \(\left\{{}\begin{matrix}\sqrt{x+1}=a\ge0\\\sqrt{1-x}=b\ge0\end{matrix}\right.\)
\(\Rightarrow a+2a^2=-b^2+b+3ab\)
\(\Leftrightarrow\left(2a^2-3ab+b^2\right)+a-b=0\)
\(\Leftrightarrow\left(a-b\right)\left(2a-b\right)+a-b=0\)
\(\Leftrightarrow\left(a-b\right)\left(2a-b+1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}a=b\\2a+1=b\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\sqrt{x+1}=\sqrt{1-x}\\2\sqrt{x+1}+1=\sqrt{1-x}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\4x+5+4\sqrt{x+1}=1-x\left(1\right)\end{matrix}\right.\)
(1) \(\Leftrightarrow4\sqrt{x+1}=-4-5x\) \(\left(x\le-\dfrac{4}{5}\right)\)
\(\Leftrightarrow16\left(x+1\right)=25x^2+40x+16\)
\(\Leftrightarrow25x^2+24x=0\Rightarrow\left[{}\begin{matrix}x=0\left(loại\right)\\x=-\dfrac{24}{25}\end{matrix}\right.\)
a) ĐKXĐ: \(x^2+3x\ge0\Leftrightarrow\left[{}\begin{matrix}x\ge0\\x\le-3\end{matrix}\right.\).
PT \(\Leftrightarrow10-\left(x^2+3x\right)=3\sqrt{x^2+3x}\). (*)
Đặt \(\sqrt{x^2+3x}=a\ge0\).
\((*)\Leftrightarrow a^2+3a-10=0\)
\(\Leftrightarrow\left(a-2\right)\left(a+5\right)=0\Leftrightarrow\left[{}\begin{matrix}a=2\\a=-5\left(l\right)\end{matrix}\right.\).
Với \(a=2\Rightarrow\sqrt{x^2+3x}=2\Leftrightarrow x^2+3x-4=0\Leftrightarrow\left(x-1\right)\left(x+4\right)=0\Leftrightarrow\left[{}\begin{matrix}x=1\left(TM\right)\\x=-4\left(TM\right)\end{matrix}\right.\).
Vậy x = 1; x = -4