Nhanh vậy, đã đạo hàm rồi
a/ \(y'=\dfrac{\left(2x+1\right)'\left(x+2\right)-\left(x+2\right)'\left(2x+1\right)}{\left(x+2\right)^2}\)
\(y'=\dfrac{2\left(x+2\right)-2x-1}{\left(x+2\right)^2}=\dfrac{2x-2x+3}{\left(x+2\right)^2}\)
\(y'=\dfrac{3}{\left(x+2\right)^2}=0\Rightarrow vo-nghiem\)
b/ \(y=\left(1-x\right)^{\dfrac{1}{2}}+\left(1+x\right)^{\dfrac{1}{2}}\Rightarrow y'=\dfrac{1}{2}\left(1-x\right)^{-\dfrac{1}{2}}+\dfrac{1}{2}\left(1+x\right)^{-\dfrac{1}{2}}=0\)
\(\Leftrightarrow\dfrac{1}{\sqrt{1-x}}+\dfrac{1}{\sqrt{1+x}}=0\Leftrightarrow\dfrac{\sqrt{1+x}+\sqrt{1-x}}{\sqrt{1-x^2}}=0\)
\(DKXD:-1< x< 1\)
\(\sqrt{1+x}+\sqrt{1-x}=0\Leftrightarrow1+x+1-x=-2\sqrt{1-x^2}\)
\(\Leftrightarrow\sqrt{1-x^2}=-1\Rightarrow vo-nghiem\)
Ủa sao vô nghiệm hết vậy chời :v?
