25.(1)在數(shù)軸上標(biāo)出數(shù)-4.5,-2,1,3.5所對(duì)應(yīng)的點(diǎn)A,B,C,D;
(2)C,D兩點(diǎn)間距離=
;B,C兩點(diǎn)間距離=
;
(3)數(shù)軸上有兩點(diǎn)M,N,點(diǎn)M對(duì)應(yīng)的數(shù)為a,點(diǎn)N對(duì)應(yīng)的數(shù)為b,那么M,N兩點(diǎn)之間的距離=
;
(4)若動(dòng)點(diǎn)P,Q分別從點(diǎn)B,C同時(shí)出發(fā),沿?cái)?shù)軸負(fù)方向運(yùn)動(dòng);已知點(diǎn)P的速度是每秒1個(gè)單位長(zhǎng)度,點(diǎn)Q的速度是每秒2個(gè)單位長(zhǎng)度,問(wèn):
①t為何值時(shí)P,Q兩點(diǎn)重合?
②t為何值時(shí)P,Q兩點(diǎn)之間的距離為1?