Question

ax^3+bx+12 chia hết cho (x-1-)(x+2)

Answer 1

Để \(f\left(x\right)=ax^3+bx+12\) chia hết cho \(\left(x-1\right)\left(x+2\right)\) thì

\(\left\{{}\begin{matrix}f\left(1\right)=a+b+12=0\\f\left(-2\right)=-8a-2b+12=0\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}f\left(1\right)=a+b=-12\\f\left(-2\right)=-2\left(4a+b\right)=-12\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}f\left(1\right)=a+b=-12\\f\left(-2\right)=4a+b=6\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}a=6\\b=-18\end{matrix}\right.\)

Sai thông cảm cho tớ nha^.^! Chúc bạn hc tốt~.~