(a+b)2-______=(a-b)2.
设所求的空为x,则x=(a+b)2-(a-b)2=4ab.
如图所示,在点电荷电场中的一条电场线上依次有A、B、C三点,分别把+q和-q的试验电荷依次放在三点上,关于它所具有的电势能的正确说法是
A.放上+q时,它们的电势能EPA>EPB>EPC
B.放上+q时,它们的电势能EPA<EPB<EPC
C.放上-q时,它们的电势能EPA>EPB>EPC
D.放上-q时,它们的电势能EPA<EPB<EPC
Bill wasn't happy about the delay of the report by Jason, and ___________.[ ]
A. I was neither
B. neither was I
C. I was either
D. either was I