Solve for a4 a_4=(-1)^(4+1)*4^2

$a_{4} = {(- 1)}^{4 + 1} \cdot 4^{2}$

Add $4$ and $1$ .

$a_{4} = {(- 1)}^{5} \cdot 4^{2}$

Raise $- 1$ to the power of $5$ .

$a_{4} = - 1 \cdot 4^{2}$

Raise $4$ to the power of $2$ .

$a_{4} = - 1 \cdot 16$

Multiply $- 1$ by $16$ .

$a_{4} = - 16$