\(1,\)\(x=0\Rightarrow P\left(0\right)=0^3+2.0^2-3.0=0\) (nhận)
\(x=1\Rightarrow P\left(1\right)=1^3+2.1^2-3.1=0\) (nhận)
\(x=-1\Rightarrow P\left(-1\right)=\left(-1\right)^3+2.\left(-1\right)^2-3.\left(-1\right)=4\) (loại)
\(x=3\Rightarrow P\left(3\right)=3^3+2.3^2-3.3=36\) (loại)
Vậy \(x=0,x=1\) là nghiệm của P(x).
\(2,\)
\(a,A\left(x\right)=2+x\)
Đặt \(A\left(x\right)=0\Rightarrow2+x=0\Rightarrow x=-2\)
\(b,B\left(y\right)=-3y+\dfrac{3}{4}\)
Đặt \(B\left(y\right)=0\Rightarrow-3y+\dfrac{3}{4}=0\Rightarrow-3y=-\dfrac{3}{4}=1=\dfrac{1}{4}\)
\(c,C\left(x\right)=x^2+2x\)
Đặt \(C\left(x\right)=0\Rightarrow x^2+2x=0\)
\(\Leftrightarrow x\left(x+2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x+2=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-2\end{matrix}\right.\)
\(d,D\left(x\right)=2x^2-6x\)
Đặt \(D\left(x\right)=0\Rightarrow2x^2-6x=0\Leftrightarrow2x\left(x-3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}2x=0\\x-3=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=3\end{matrix}\right.\)
