zouruofei
幼苗
共回答了18个问题采纳率：94.4% 举报
a(x^3 - x^2 - 3x) + b(2x^2 + x) + x^3 - 5
= (a+1)x^3 + (2b-a)x^2 + (b-3a)x - 5.
a + 1 = 0,a = -1.
2次多项式化为,
(2b+1)x^2 + (b+3)x - 5,
25 = (2b+1)4 + (b+3)2 - 5,
10b = 20,
b = 2,
2次多项式化为,
5x^2 + 5x - 5
x = -2时,该多项式的值 = 5*4 + 5(-2) - 5 = 5
1年前
10
