A:重晶石:BaCO3
B:石膏:CaSO4·2H2O
C:芒硝:Na2SO4·10H2O
D:绿矾:FeSO4·7H2O
带着好心情走进考场,告诉自己“静下心来、沉住气,我一定能行。”这种调节情绪的方法是( )
﹣1=﹣1.
﹣1+3=2,
﹣1+3﹣5=﹣3,
﹣1+3﹣5+7=4
…
则﹣1+3﹣5+7…+(﹣1)n(2n﹣1)=____.
— You think studying English well is difficult, but we know interest can be any way.
一 Thank you for your advice.