We know that the image of quadratic function passes through three points a (1,3) B (- 1,5) C (2, - 1) I can't do my homework... Help me...
Let the analytic expression of quadratic function be y = ax ^ 2 + BX + C
Substituting a (1,3) B (- 1,5) C (2, - 1) into a (1,3) B (- 1,5) C (2, - 1) gives the following formula:
a+b+c=3 (1)
a-b+c=5 (2)
4a+2b+c=-1 (3)
(1)-(2):
2b=-2 ==> b=-1
a+c=4
4a+c= 1
a=-1,c=5
The analytic expression of quadratic function is y = - x ^ 2-x + 5
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