Explanation

From x² = y+z, adding x to both sides gives x(x+1) = x+y+z; call this sum S. Hence 1/(x+1) = x/S, and similarly 1/(y+1) = y/S and 1/(z+1) = z/S. Adding gives (x+y+z)/S = 1 (option B), valid as long as none of x, y, z equals −1.