若方程x2-4x+m=0有两个相等的实数根,则m的值是______.
∵方程x2-4x+m=0有两个相等的实数根,
∴△=b2-4ac=16-4m=0,
解之得,m=4
故本题答案为:4
The dead rate is _____ pigs and recovery usually ______ within 7-10 days.
A low in; occurs B.rich in;happens
C.high in; came about D.poor in;took place
控制焊接残余变形的措施有哪些?