解答

Choosen As Best Answer

1.
4x^2 +4x +1 = 998
4x^3 -1001x -1000 ÷ 4x^2 -4x +1 = x +1 ... -998x -1001
=>
4x^3 -1001x -1000 = (4x^2 -4x +1)(x +1) + (-998x -1001)
= 998(x+1) -998x -1001
= -3
所求 = (-3)^4 = 81

2.
(x+5)^2 = x^2 +10x +25 = 0 兩邊同除以10
1/10 x^2 +x + 25/10 = 0
2a -c = 2/10 - 25/10 = -23/10

3.
把 x = -2 代入,整理後:
5a^2 -10a +2 = 0 用公式解
a = 5±√15 / 5

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