Originally Posted by

**jonah** $\displaystyle

\begin{gathered}

10,000\left( {1 + i} \right)^2 + 3,500\left( {1 + i} \right) = 15,569.75 \hfill \\

\Leftrightarrow \hfill \\

\end{gathered}

$

$\displaystyle

\begin{gathered}

\left[ {10,000\left( {1 + i} \right) + 3,500} \right]\left( {1 + i} \right) = 15,569.75 \hfill \\

\Leftrightarrow \hfill \\

\end{gathered}

$

$\displaystyle

\begin{gathered}

\left[ {10,000 + 10,000i + 3,500} \right]\left( {1 + i} \right) = 15,569.75 \hfill \\

\Leftrightarrow \hfill \\

\end{gathered}

$

$\displaystyle

10,000 + 10,000i + 3,500 + 10,000i + 10,000i^2 + 3,500i = 15,569.75

$

You need the quadratic formula.