Direct image of a set for a function definded on $\mathbb{R}^2$ to $\mathbb{R}$ defined by $f((x,y))=x-9$ 

i want to find $f(A)$ where $$A=\{(x,y)\in\mathbb{R}^2, (x-1)^2+(y+1)^2&lt;1\}$$

How to do ?

Can i say that $$f(A)=]1-\sqrt{1-(y+1)^2}, 1+\sqrt{1-(y+1)^2}[$$ with $-2&lt;y&lt;0$
Hint: if $(x,y) \in A$, then $-2&lt;x&lt;0$ hence $-11 &lt;f(x,y)&lt;-9$.
Hint: if $(x,y) \in A$, then $-2&lt;x&lt;0$ hence $-11 &lt;f(x,y)&lt;-9$.