0所以与x轴总有两个不同交点2)设交x轴于x1和x" property="og:description"/>
1)
△ = a" -4(a-2) = a"-4a+8 = a"-4a+4+4 = (a-2)"+4>0
所以与x轴总有两个不同交点
2)设交x轴于x1和x2(x1