Maths(方程)

a+b+c+d=1 ................(1)
8a+4b+2c+d=1...........(2)
27a+9b+3c+d=-5 .......(3)
64a+16b+4c+d=-23....(4)
(2) - (1) :
7a + 3b + c = 0 ........(5)(3) - (2) :
19a + 5b + c = - 6 ....(6)(4) - (3) :
37a + 7b + c = - 18 ...(7)
(6) - (5) :
12a + 2b = - 6
6a + b = - 3..............(8)(7) - (6) :
18a + 2b = - 12
9a + b = - 6..............(9)
(9) - (8) :
3a = - 3a = - 1 , 代入(8) :b = 3 , 代入(6) :19(-1) + 5(3) + c = - 6c = - 2 , 代入 (1) :- 1 + 3 - 2 + d = 1d = 1

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