Question 12Let $f$ be the function defined by $f(x)=ax^2-\sqrt2$ for some positive $a.$ If $f(f(\sqrt2))=-\sqrt2,$ then $a=$$\frac{2-\sqrt2}{2}$$\frac12$$2-\sqrt2$$\frac{\sqrt2}{2}$$\frac{2+\sqrt2}{2}$