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1. TXĐ:
a. \(D=R\)
b. \(4x^2+5x-9\ne0\Rightarrow\left[{}\begin{matrix}x\ne1\\x\ne-\dfrac{9}{4}\end{matrix}\right.\) \(\Rightarrow D=R\backslash\left\{-\dfrac{9}{4};1\right\}\)
c. \(D=R\)
d. \(\left\{{}\begin{matrix}x+2\ne0\\x+4\ge0\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}x\ge-4\\x\ne-2\end{matrix}\right.\) \(\Rightarrow D=[-4;+\infty)\backslash\left\{-2\right\}\)
e. \(\left\{{}\begin{matrix}3-x\ge0\\x^2-5x+4\ne0\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}x\le3\\x\ne1\\x\ne4\end{matrix}\right.\) \(\Rightarrow D=(-\infty;3]\backslash\left\{1\right\}\)
f. \(\left\{{}\begin{matrix}x-1>0\\5-2x>0\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}x>1\\x< \dfrac{5}{2}\end{matrix}\right.\) \(\Rightarrow D=\left(1;\dfrac{5}{2}\right)\)
2.
\(1>0\Rightarrow f\left(1\right)=\dfrac{1+1}{1^2+1+1}=\dfrac{2}{3}\)
\(f\left(0\right)=0^2-2.0-1=-1\)
\(-2< 0\Rightarrow f\left(-2\right)=\left(-2\right)^2-2.\left(-2\right)-1=7\)
