24.如圖,A在數(shù)軸上所對(duì)應(yīng)的數(shù)為-2.
(1)點(diǎn)B在A的右邊,距離A點(diǎn)7個(gè)單位長(zhǎng)度,則點(diǎn)B所對(duì)應(yīng)的數(shù)是
;
(2)在(1)的條件下,點(diǎn)A以每秒2個(gè)單位長(zhǎng)度沿?cái)?shù)軸向左運(yùn)動(dòng),同時(shí)點(diǎn)B以每秒3個(gè)單位長(zhǎng)度沿?cái)?shù)軸也向左運(yùn)動(dòng).
①當(dāng)點(diǎn)A運(yùn)動(dòng)到-6所在的點(diǎn)處時(shí),點(diǎn)B停止運(yùn)動(dòng),此時(shí)A,B兩點(diǎn)的距離是
;
②求經(jīng)過多長(zhǎng)時(shí)間A,B兩點(diǎn)相距4個(gè)單位長(zhǎng)度.