Discrete Mathematics with Applications 4th Edition

$11$
The lower limit of $k$ is $-1$ and the upper limit is $1$. Thus, evaluate the given summation from $k=-1$ to $k=1$ to obtain: $=[(-1)^2+3] + (0^2+3) + (1^2+3) \\=(1+3)+(0+3) + (1+3) \\=4+3+4 \\=11$