3.已知直線l:y=kx+b經(jīng)過點(diǎn)(0,7)和點(diǎn)(1,6).
(1)求直線l的解析式;
(2)若點(diǎn)P(m,n)在直線l上,以點(diǎn)P為頂點(diǎn)的拋物線G過點(diǎn)(0,-3)且開口向下.
①求m的取值范圍.
②設(shè)拋物線G與直線l的另一個(gè)交點(diǎn)為Q.當(dāng)點(diǎn)Q向左平移1個(gè)單位長度得到點(diǎn)Q'也在G上時(shí),求G在
≤x≤
+1的圖象的最高點(diǎn)的坐標(biāo).