24.如圖,直線l
1經(jīng)過點(diǎn)P(2,2),分別交x軸、y軸于點(diǎn)A(4,0),B.
(1)求直線l
1的解析式;
(2)點(diǎn)C為x軸負(fù)半軸上一點(diǎn),過點(diǎn)C的直線l
2:y=mx+n交線段AB于點(diǎn)D.
①如圖1,當(dāng)點(diǎn)D恰與點(diǎn)P重合時(shí),點(diǎn)Q(t,0)為x軸上一動點(diǎn),過點(diǎn)Q作QM⊥x軸,分別交直線l
1、l
2于點(diǎn)M、N.若m=
,MN=2MQ,求t的值;
②如圖2,若BC=CD,試判斷m,n之間的數(shù)量關(guān)系并說明理由.