\(y=\left(2sinx+1\right)^2+1\ge1\)
\(y_{min}=1\) khi \(sinx=-\dfrac{1}{2}\)
\(y=4\left(sin^2x+sinx-2\right)+8=4\left(sinx-1\right)\left(sinx+2\right)+8\)
Do \(\left\{{}\begin{matrix}sinx-1\le0\\sinx+2>0\end{matrix}\right.\) ;\(\forall x\Rightarrow\left(sinx-1\right)\left(sinx+2\right)\le0\)
\(\Rightarrow y\le8\)
\(y_{max}=8\) khi \(sinx=1\)