y=ax^2+bx+c的图像y的最小值为-3最小值 =>a>0y=ax^2+bx+c=a(x+b/2a)^2+(4ac-b^2)/4a(4ac-b^2)/4a=-3 => b^2=4a(c+3)ax^2+bx+c+2=0 =>ax^2+bx+c=-2>-3 => 方程有两个解 x=[-b+(或-)√(b^2-4a(c+2))]/2a=[-b+(或-)2√a...