3. Given the equation $x^{2}+(a-2) x+a+1=0$ with two complex roots $x_{1}, x_{2}$, and the point $\left(x_{1}, x_{2}\right)$ lies on the circle $x^{2}+y^{2}=4$. Then the value of $a$ $=$ $\qquad$
$3.3-\sqrt{11}$