已知等式y=ax²+bx+c,且当x=-1时y=0,当x=2时y=3,当x=-5时y=-60,你能求出a,b,
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![已知等式y=ax²+bx+c,且当x=-1时y=0,当x=2时y=3,当x=-5时y=-60,你能求出a,b,](/uploads/image/z/4504157-53-7.jpg?t=%E5%B7%B2%E7%9F%A5%E7%AD%89%E5%BC%8Fy%3Dax%26%23178%3B%2Bbx%2Bc%2C%E4%B8%94%E5%BD%93x%3D-1%E6%97%B6y%3D0%2C%E5%BD%93x%3D2%E6%97%B6y%3D3%2C%E5%BD%93x%3D-5%E6%97%B6y%3D-60%2C%E4%BD%A0%E8%83%BD%E6%B1%82%E5%87%BAa%2Cb%2C)
已知等式y=ax²+bx+c,且当x=-1时y=0,当x=2时y=3,当x=-5时y=-60,你能求出a,b,
已知等式y=ax²+bx+c,且当x=-1时y=0,当x=2时y=3,当x=-5时y=-60,你能求出a,b,
已知等式y=ax²+bx+c,且当x=-1时y=0,当x=2时y=3,当x=-5时y=-60,你能求出a,b,
答案:a=-2,b=3,c=5
将当x=-1时y=0,当x=2时y=3,当x=-5时y=-60分别代入原方程,
可得:a-b+c=0 (1)
4a+2b+c=3 (2)
25a-5b+c=-60 (3)
将(2)-(1)可得:3a+3b=3
即:a+b=1 (4)
将(3)-(2)可得:21a-7b=-63
即:3a-b=-9 (5)
(4)+(5)可得:4a=-8 即a=-2
将a=-2代入(4)可得:b=3
将a=-2,b=3代入(1)可得:c=5
综上可得:
a=-2,b=3,c=5