gpt
\(4\sqrt{x+4}+\sqrt{16-3x}=x^2+4x+12\)
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ĐKXĐ: \(-\frac{16}{3}\le x\le4\)
\(\Leftrightarrow3x^2-12x+36=12\sqrt{4-x}+3\sqrt{3x+16}\)
\(\Leftrightarrow3x^2-9x+4\left(6-x-3\sqrt{4-x}\right)+\left(x+12-3\sqrt{3x+16}\right)=0\)
\(\Leftrightarrow3\left(x^2-3x\right)+\frac{4\left(x^2-3x\right)}{6-x+3\sqrt{4-x}}+\frac{x^2-3x}{x+12+3\sqrt{3x+16}}=0\)
\(\Leftrightarrow\left(x^2-3x\right)\left(3+\frac{4}{6-x+3\sqrt{4-x}}+\frac{1}{x+12+3\sqrt{3x+16}}\right)=0\)
\(\Leftrightarrow x^2-3x=0\)
ĐLXĐ:\(x\ge-1\)
\(\sqrt{x^2+4x+12}=2x-4+\sqrt{x+1}\)
\(\Leftrightarrow\left[\sqrt{x^2+4x+12}-\left(6-3x\right)\right]-\left[\sqrt{x+1}-\left(x-2\right)\right]=0\)
\(\Leftrightarrow\frac{x^2+4x+12-36+36x-9x^2}{\sqrt{x^2+4x+12}+2-3x}-\frac{x+1-x^2+4x-4}{\sqrt{x+1}+x+2}=0\)
\(\Leftrightarrow\frac{-8x^2+40x-24}{\sqrt{x^2+4x+12}+2-3x}-\frac{-x^2+5x-3}{\sqrt{x+1}+x-2}=0\)
\(\Leftrightarrow\frac{8\left(-x^2+5x-3\right)}{\sqrt{x^2+4x+12}+2-3x}-\frac{-x^2+5x-3}{\sqrt{x+1}+x-2}=0\)
\(\Leftrightarrow\left(-x^2+5x-3\right)\left[\frac{8}{\sqrt{x^2+4x+12}+2-3x}-\frac{1}{\sqrt{x+1}+x-2}\right]=0\)
TH1:\(-x^2+5x-3=0\Rightarrow\orbr{\begin{cases}x=\frac{5+\sqrt{13}}{2}\\x=\frac{5-\sqrt{13}}{2}\end{cases}}\)
TH2:........ ( chắc vô nghiệm )
b,\(\sqrt{16\left(x+1\right)}-\sqrt{9\left(x+1\right)}+\sqrt{4\left(x+1\right)}-16\sqrt{x+1}=0\) (dk \(x\ge-1\)
\(\Leftrightarrow\sqrt{x+1}\left(4-3+2-16\right)=0\)
\(\Leftrightarrow\sqrt{x+1}.-13=0\)
\(\Leftrightarrow x=-1\)
<=>\(\sqrt{3\left(x+1\right)^2+9}+\sqrt{5\left(x^2-1\right)^2+4}+2\left(x+1\right)^2=5\)
mà \(\sqrt{3\left(x+1\right)^2+9}\ge3\), \(\sqrt{5\left(x^2-1\right)^2+4}\ge4\), \(2\left(x+1\right)^2\ge0\)với mọi x
=>\(\sqrt{3\left(x+1\right)^2+9}+\sqrt{5\left(x^2-1\right)^2+4}+2\left(x+1\right)^2\ge3+2+0=5\)
'=" xảy ra<=> x+1=0<=> x=-1