Let the circle C_1: x^2+y^2-2(x+y)+1=0 and C_2 be a circle having centre at (-1,0) and radius 2. If the line of the common chord of C_1 and C_2…

Let the circle $\displaystyle C_1: x^2+y^2-2(x+y)+1=0$ and $\displaystyle C_2$ be a circle having centre at $\displaystyle (-1,0)$ and radius $\displaystyle 2$ . If the line of the common chord of $\displaystyle \mathrm{C}_1$ and $\displaystyle \mathrm{C}_2$ intersects the $\displaystyle y$-axis at the point P , then the square of the distance of P from the centre of $\displaystyle \mathrm{C}_1$ is :