ANSWER
[tex]f(x) = 2 ({x - 1)}^{2} - 1[/tex]
EXPLANATION
The vertex form of a parabola has equation:
[tex]f(x) = a ({x - h)}^{2} + k[/tex]
where V(h,k) is the vertex of the parabola and 'a' is the leading coefficient.
From the question, we have that, the vertex is
[tex](1,-1)[/tex]
and the leading coefficient is
[tex]a= 2[/tex]
We substitute the vertex and the leading coefficient into the vertex form to get:
[tex]f(x) = 2 ({x - 1)}^{2} + - 1[/tex]
We simplify to get:
[tex]f(x) = 2 ({x - 1)}^{2} - 1[/tex]
The graph of this function is shown in the attachment.
