28.在數(shù)軸上,點(diǎn)A表示的數(shù)為a,點(diǎn)B表示的數(shù)為b,且|a+2|+(b-3)
2=0.
(1)a=
,b=
;
(2)在(1)的條件下,點(diǎn)A以每秒0.5個(gè)單位長度沿?cái)?shù)軸向左移動,點(diǎn)B以每秒1個(gè)單位長度沿?cái)?shù)軸向右移動,兩點(diǎn)同時(shí)移動,當(dāng)點(diǎn)A運(yùn)動到-4所在的點(diǎn)處時(shí),求A、B兩點(diǎn)間距離;
(3)在(2)的條件下,現(xiàn)A點(diǎn)靜止不動,B點(diǎn)沿?cái)?shù)軸向左運(yùn)動時(shí),經(jīng)過多長時(shí)間A、B兩點(diǎn)相距3個(gè)單位長度?