抛物线y=ax^2-3ax+b经过点(-1,0)(3.2),

抛物线y=ax^2-3ax+b经过点(-1,0)(3.2),
抛物线y=ax^2-3ax+b经过点(-1,0)(3.2),

抛物线y=ax^2-3ax+b经过点(-1,0)(3.2),
点(-1,0)(3.2)坐标代入得:
0=a+3a+b=4a+b
2=9a-6a+b=3a+b
解得:a=-2,b=8
y=-2x^2+6x+8

直接把两个点分别代入就可以了