\(\Leftrightarrow x\left(x^2-5\right)=0\\ \Leftrightarrow x\left(x-\sqrt{5}\right)\left(x+\sqrt{5}\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x=\sqrt{5}\\x=-\sqrt{5}\end{matrix}\right.\)

Diện tích rừng là \(0,5\times0,5\times2=0,5\left(km^2\right)\)

\(a,\text{Diện tích hcn là }24\times\left(24\times\dfrac{2}{3}\right)=384\left(m^2\right)\\ b,\text{Diện tích trồng ngô là }384\times\dfrac{2}{3}=256\left(m^2\right)\)

\(2,\text{PT hoành độ giao điểm: }-3x-6=x+3\Leftrightarrow x=-\dfrac{9}{4}\Leftrightarrow y=\dfrac{3}{4}\Leftrightarrow A\left(-\dfrac{9}{4};\dfrac{3}{4}\right)\)

Bài 2:

\(a,A=\dfrac{\dfrac{1}{2}+2}{2\cdot\dfrac{1}{4}+1}=\dfrac{\dfrac{5}{2}}{\dfrac{1}{2}+1}=\dfrac{\dfrac{5}{2}}{\dfrac{3}{2}}=\dfrac{5}{3}\\ b,B=\dfrac{x-\sqrt{x}-2-2\sqrt{x}-4+6+\sqrt{x}}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}\\ B=\dfrac{x-2\sqrt{x}}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}=\dfrac{\sqrt{x}\left(\sqrt{x}-2\right)}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}=\dfrac{\sqrt{x}}{\sqrt{x}+2}\)

Vì \(\sqrt{x}\ge0;\sqrt{x}+2>0\Leftrightarrow B>0,\forall x\Leftrightarrow\left|B\right|=B\)

\(a,R=\dfrac{2x+1-x+\sqrt{x}}{\left(\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)}\cdot\left[\dfrac{\left(1+\sqrt{x}\right)\left(x-\sqrt{x}+1\right)}{1+\sqrt{x}}-\sqrt{x}\right]\\ R=\dfrac{\left(x+\sqrt{x}+1\right)\left(x-2\sqrt{x}+1\right)}{\left(\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)}\\ R=\dfrac{\left(\sqrt{x}-1\right)^2}{\sqrt{x}-1}=\sqrt{x}-1\\ b,R=3\Leftrightarrow\sqrt{x}=4\Leftrightarrow x=16\left(tm\right)\)

Phản ứng giữa dung dịch \(Ca\left(OH\right)_2\) và dung dịch \(HCl\) (vừa đủ) thuộc loại: