一元二次方程(x+1)(x+4)=0的解是 x1=-1,x2=-4.
(x+1)(x+4)=0,
∴x+1=0或x+4=0,
解得x1=-1,x2=-4.
故答案为:-1,-4.
The little girl _____ go out at night and often imagined _____ a monster following her
A.dared not;there being
B.dare not;there being
C.did not dare;there to be
D.didn’t dare to;there be
转轮叶片进、出口水流绝对速度,分别用字母()表示。
A、vr1和vr2;
B、w1和w2;
C、v1和v2;
D、v2和v1。