当a( )时,a²大于2a;当a( )时a²<2a;当a( )时a²=2a当a( )时,a²大于2a;当a( )时a²<2a;当a( )时a²=2a
当a( )时,a²大于2a;当a( )时a²<2a;当a( )时a²=2a0
a>2或者a<0; 0