From F (-4) = 16-4 B+C = C, F (-2) = 4-2 B+C =-2, b=4, c=2.f(x)=x? +4x+2(x≤0)，f(x)= 2(x & gt； 0)

The zero point of that function g(x)=f(x)-x can be regard as the intersection of the straight line y=x and the image of the piecewise function. * * * has three intersections, which means there are three zeros.