当m______时，（m-1）x2+2mx+m+1=0是一元二次方程．
由一元二次方程的定义可得m-1≠0，即m≠1．
看图，联系实际给下列句子标号。
( ) Wait for a flower to grow.
( ) Plant the seeds in the soil.
( ) Add water often.
( ) Wait for a sprout.
( ) Put the pot under the sun.
A．a为动滑轮，B端钢缆受到滑轮组的拉力大小约为3G
B．a为动滑轮，B端钢缆受到滑轮组的拉力大小约为G
C．a、c为动滑轮，B端钢缆受到滑轮组的拉力大小约为3G
D．a、c为动滑轮，B端钢缆受到滑轮组的拉力大小约为G
G
G