A:(a+2)(a﹣2)=a2﹣2
B:(a+1)(a﹣2)=a2+a﹣2
C:(a+b)2=a2+b2
D:(a﹣b)2=a2﹣2ab+b2
设fx=x3+log2x+x2+1,则对任意实数a,b,a+b≥0是fa+fb≥0的( )