For certain real numbers $a$, $b$, and $c$, the polynomial \[g(x) = x^3 + ax^2 + x + 10\]has three distinct roots, and each root of $g(x)$ is also a root of the polynomial \[f(x) = x^4 + x^3 + bx^2 + 100x + c.\]What is $f(1)$?
$\textbf{(A)}\ -9009 \qquad\textbf{(B)}\ -8008 \qquad\textbf{(C)}\ -7007 \qquad\textbf{(D)}\ -6006 \qquad\textbf{(E)}\ -5005$
$f(x)$ must have four roots, three of which are roots of $g(x)$. Using the fact that every polynomial has a unique factorization into its roots, and since the leading coefficient of $f(x)$ and $g(x)$ are the same, we know that
\[f(x)=g(x)(x+p)\]
where $-p\in\mathbb{R}$ is the fourth root of $f(x)$. 
(Using $(x+p) = (x-r))$ instead of $(x-r)$ makes the following computations less messy.)
Substituting $g(x)$ and expanding, we find that
\begin{align*}f(x)&=(x^3+ax^2+x+10)(x+p)\\ &=x^4+(a+p)x^3+(1+ap)x^2+(10+p)x+10r.\end{align*}
Comparing coefficients with $f(x)$, we see that
\begin{align*} a+p&=1\\ 1+ap=b\\ 10+p&=100\\ 10p&=c.\\ \end{align*}

Let's solve for $a,b,c,$ and $p$. Since $10+p=100$, $p=90$.
Since $a+p=1$, $a=-89$. 
(Solution 1.1 branches from here and takes a shortcut.)
$c=(10)(90)=900$.
Then, since $b=1+ap$, $b=-8009$. Thus,
\[f(x)=x^4+x^3-8009x^2+100x+900.\]
(Solution 1.2 branches from here and takes another shortcut)
Taking $f(1)$, we find that
\begin{align*} f(1)&=1^4+1^3-8009(1)^2+100(1)+900\\ &=1+1-8009+100+900\\ &=\boxed{\bold{(C)}\, -7007}.\\ \end{align*}

Solution 1.1
A faster ending to Solution 1 is as follows.
\begin{align*} f(1)&=(1+p)(1^3+a\cdot1^2+1+10)\\ &=(91)(-77)\\ &= (7)(13)(11)(-7) = (1001)(-7) \\ &=\boxed{\bold{(C)}\, -7007}.\\ \end{align*}

Solution 1.2
Also a faster ending to Solution 1 is as follows.
To find $f(1)$ we just need to find the sum of the coefficients which is $1 + 1 - 8009 + 100 + 900= \boxed{\bold{(C)} \ , -7007}.$
~[Yiyj1](https://artofproblemsolving.com/wiki/index.php/User:Yiyj1)