giải hộ khí vl

$\displaystyle  \begin{array}{{>{\displaystyle}l}}
f( x) =\int f'( x) dx\\
\Leftrightarrow f( x) =\int 12x^{2} +2dx\\
\Leftrightarrow f( x) =4x^{3} +2x+C
\end{array}$
mà $\displaystyle f( 1) =3$
$\displaystyle  \begin{array}{{>{\displaystyle}l}}
\Rightarrow 4+2+C=3\\
\Leftrightarrow C=-3\\
\Rightarrow f( x) =4x^{3} +2x-3
\end{array}$
Ta có:
$\displaystyle  \begin{array}{{>{\displaystyle}l}}
F( x) =\int f( x) dx\\
\Leftrightarrow F( x) =\int 4x^{3} +2x-3dx\\
\Leftrightarrow F( x) =x^{4} +x^{2} -3x+C
\end{array}$
mà $\displaystyle F( 0) =2\Rightarrow C=2$
$\displaystyle  \begin{array}{{>{\displaystyle}l}}
\Rightarrow F( x) =x^{4} +x^{2} -3x+2\\
F( 1) =1
\end{array}$