A:牛奶
B:豆浆
C:冰水
D:糖水
∠ACB=∠BDC=45°,DC = 3 ,求:
_______ there any flowers in the nature park? ( )
函数f(x)满足4f(x)f(y)=f(x+y)+f(x-y)x,y∈R,且f1=14,f0≠0,则下列等式不成立的是( )