②△=b？ -4ac=36-4×2×5=-4。 If there is no root, choose C.

③ If the equation holds when x =-1, then one of them must be-1.

X=b becomes x? +cx+b=0，b？ +bc+b=0, then

B+c+ 1=0, that is, b+c=- 1.

Four aces? +b？ =x, then x(x- 1)=20,

x？ -x-20=0, that is, (x+4)(x-5)=0,

X=-4 or x=5.

It's clearly a? +b？ ≦-4, what about A? +b？ =5。

⑤ When is△ = (-2)? The equation -4k=4( 1-k)≥0 has a real root,

That is, 1-k≥0, then k≤ 1, k≠ 1(x? Coefficient is not 0)