已知点C是AB的黄金分割点(AC>BC),若AB=4cm,则AC的长为( ).
A:(2 -2)cm
B:(6-2 )cm
C:( -1)cm
D:(3- )cm
work on, talk about, be ready for, make a joke, have a rest
方程x2-3x+4=0的根的情况是( )