We ________ oxygen _______ the air and release ( 释放 ) CO2 into the air.
门第不高的读书人可以凭才学参政始于( )
设函数f(x)=ax2+bx+c且f(1)=﹣a2,3a>2c>2b.
(1)试用反证法证明:a>0
(2)证明:﹣3<ba<-34.