已知關(guān)于x的方程mx2-3(m-1)x+2m-3=0.
(1)求證:無論m取任何實數(shù)時,方程總有實數(shù)根;
(2)若關(guān)于x的二次函數(shù)y1=mx2-3(m-1)x+2m-3的圖象關(guān)于y軸對稱.
①求這個二次函數(shù)的解析式;
②已知一次函數(shù)y2=2x-2,證明:在實數(shù)范圍內(nèi),對于x的同一個值,這兩個函數(shù)所對應(yīng)的函數(shù)值y1≥y2均成立;
(3)在(2)的條件下,若二次函數(shù)y3=ax2+bx+c的圖象經(jīng)過點(-5,0),且在實數(shù)范圍內(nèi),對于x的同一個值,這三個函數(shù)所對應(yīng)的函數(shù)值y1≥y3≥y2均成立.求二次函數(shù)y3=ax2+bx+c的解析式.