已知(a2+b2+1)2=4,求a2+b2的值。
解:a2+b2+1=±2
∴a2+b2=1, a2+b2=-3
∵a2≥0,b2≥0
∴a2+b2≥0
∴a2+b2=1
It was playing computer games that cost the boy plenty of time that he ______ spent doing his lessons.
A.might have
B.should
C.ought to have
D.could
衡量和评价公司购入存款、投入生产、销售收回等环节管理状况的指标是( )。
A.存货周转率 B.应收账款周转率C.流动资产周转率 D.总资产周转率