∵x>0,
∴x2+2x=x+2x
≥2x•2x=22.
当且仅当x=2x即x=2时取等号,
故选B.
一 How are you?
— _____ [ ]
A. How are you
B. Thank you
C. It's OK
D. Fine, thanks
从所给的四个选项中,选择最合适的一个填入问号处,使之呈现一定的规律性。()
A.选项A
B.选项B
C.选项C
D.选项D