一元二次方程x2+3x=0的解是x1=______,x2=______.(x1>x2)
∵x2+3x=0,即x(x+3)=0,
⇒x=0或x+3=0,
解得x1=0,x2=-3.
句型转换。
1. He looks like his mother. (改为同义句)
He and his mother ________ ________ ________.
2. He took good care of his dog.(改为同义句)
He ________ ________ his dog________.
3. I'm not healthy. (改为同义句)
I'm ________
4. Although they were poor, they bought many books.(改为同义句)
They were poor, ________ they bought many books.
5. 或许他是对的。
________ he is right. =He________ ________ right.
灰将泵的叶轮使用周期一般在()h左右。
A.700~1500;
B.1500~2000;
C.2000~2500;
D.2500~3000。