## Intermediate Algebra for College Students (7th Edition)

$j(x)=-x^2-1$.
If the vertex of a quadratic function is at $(k,m)$. Then its equation can be $f(x)=\pm(x-k)^2+m$. $+$ if it is open up, $-$ if it is open down. Hence here the function is $j(x)=-x^2-1$.