I want to solve 3.c)

the answer is \(- {209 715 \over 256}\), what am i doing wrong?

how am i solving this geometric series wrong?

\(\begin{array}{|rcll|} \hline && (-4)^{10} \\ &=& {\color{red}+}4^{10} \qquad \text{ because the exponent is even!} \\ &=& 1048576 \\ \hline \end{array} \)

C)

Sum = 1/256 x [ 1 - (-4)^10] / [1 - (-4)]

Sum = 1/256 x [1 - 1,048,576] / [1 + 4]

Sum = 1/256 x [-1,048,575] / [5]

Sum = 1/256 x [ - 209,715]

Sum = - 209,715 / 256