(x-4)^2=x^2-2*x*4+4^2=x^2-8x+16a=8+3=11a=-8+3=-5
16=(±4)²则原式=(x±4)²=x²±8x+16所以-(a-3)=-8,-(a-3)=-8a-3=8,a-3=-8a=11,a=-5
