26.規(guī)定:P(x
1,y
1),Q(x
2,y
2)為函數(shù)圖象上不重合的兩點(diǎn),若PQ∥x軸,則稱(chēng)點(diǎn)P,Q互為這個(gè)函數(shù)的對(duì)“平行點(diǎn)”.
(1)函數(shù)①y
1=|x|,②y
2=2x+1,③y
3=
,其中有“平行點(diǎn)”的函數(shù)為
(填序號(hào));
(2)若點(diǎn)C(-5,y
1),D(1,y
2)為二次函數(shù)y=ax
2+bx+c圖象上的一對(duì)“平行點(diǎn)”,E(x
0,y
0)在函數(shù)圖象上,當(dāng)-2≤x
0≤1時(shí),-1≤y
0≤1,求c的值;
(3)若點(diǎn)F(1,m),G(3,n)在函數(shù)y=ax
2+bx+c(a>0)圖象上,且m<n≤c,設(shè)該函數(shù)圖象上點(diǎn)F的“平行點(diǎn)”H的橫坐標(biāo)為x
0,求-
-4x
0+2的最大值.