如果关于x的方程x2+kx+9=0有两个相等的实数根,那么k的值为______.
∵方程有两相等的实数根,
∴△=b2-4ac=k2-36=0,
解得k=±6.
故答案为±6.
For sustainable development, the government has decided to give __________ to those energy conserving and environmental-- friendly business in many aspects.
A.profit
B.interest
C.advantage
D.preference
头部横断层常用基线有眦耳线、Reid基线、连合间线等。
冠状断层标本的制作常以____线的垂线为基线()
A.连合间线
B.眦耳线
C.Reid基线
D.听眦线
E.AC-PC线