3.如圖,點(diǎn)M,N在數(shù)軸上分別位于原點(diǎn)O的左右兩邊,點(diǎn)M表示的數(shù)是a,點(diǎn)N表示的數(shù)是b,且a,b滿(mǎn)足(a+4)
2+|b-8|=0.點(diǎn)A、B、C是線段ON的四等分點(diǎn),分別以線段OA、AB、BC為邊向數(shù)軸的上方作正方形OAED,正方形ABFE,正方形BCGF.
(1)直接寫(xiě)出a,b的值:a=
,b=
;
(2)如圖1,若動(dòng)點(diǎn)P從點(diǎn)M出發(fā)以每秒3個(gè)單位長(zhǎng)度的速度沿折線M-O-D-G運(yùn)動(dòng),同時(shí)動(dòng)點(diǎn)Q從點(diǎn)N出發(fā)以每秒2個(gè)單位長(zhǎng)度的速度沿折線N-C-G-D運(yùn)動(dòng),當(dāng)點(diǎn)P到達(dá)點(diǎn)G時(shí)P,Q兩點(diǎn)同時(shí)停止運(yùn)動(dòng),設(shè)點(diǎn)P的運(yùn)動(dòng)時(shí)間為t,求線段PQ=1時(shí)t的值;
(3)如圖2,若動(dòng)點(diǎn)P從點(diǎn)M出發(fā)以每秒4個(gè)單位長(zhǎng)度的速度向數(shù)軸的正方向運(yùn)動(dòng),當(dāng)點(diǎn)P到達(dá)點(diǎn)O時(shí)立即以每秒2個(gè)單位長(zhǎng)度的速度沿折線O-D-G-D運(yùn)動(dòng),點(diǎn)P到達(dá)點(diǎn)O的同時(shí)動(dòng)點(diǎn)Q從點(diǎn)N出發(fā)以每秒2個(gè)單位長(zhǎng)度的速度向數(shù)軸的負(fù)方向運(yùn)動(dòng),當(dāng)點(diǎn)Q首次到達(dá)點(diǎn)C后立即以每秒3個(gè)單位長(zhǎng)度的速度在點(diǎn)C和點(diǎn)O之間往返運(yùn)動(dòng),過(guò)動(dòng)點(diǎn)Q作直線l垂直O(jiān)N,在運(yùn)動(dòng)過(guò)程中,直線l與線段DG的交點(diǎn)為H.當(dāng)點(diǎn)P第二次到達(dá)點(diǎn)D時(shí)P,Q兩點(diǎn)同時(shí)停止運(yùn)動(dòng).設(shè)點(diǎn)P的運(yùn)動(dòng)時(shí)間為t,直接寫(xiě)出線段PH=2時(shí)t的值.