1003261906
Level:
A
Determine the values of \( a \) and \( b \) (\( a \), \( b \in\mathbb{R} \)) such that the function
\[ f(x)=ax^3+bx^2+1 \]
has a local extremum of \( 9 \) at \( x=-2 \).
\( a=2 \), \( b=6 \)
\( a=-2 \), \( b = 6 \)
\( a=-2 \), \( b = -6 \)
\( a=2 \), \( b = -6 \)