若(x的平方+px+q)(x的平方—3x+2)的乘积中不含x的平方和x项(注:不含不含x的平方项

2025-05-01 14:00:10
推荐回答(1个)
回答1:

解:∵ (x ² + p x + q)(x ² - 3 x + 2)
= x ²(x ² - 3 x + 2)+ p x (x ² - 3 x + 2)+ q(x ² - 3 x + 2)
= x ⁴ - 3 x ³ + 2 x ² + p x ³ - 3 p x ² + 2 p x + q x ² - 3 q x + 2 q
= x ⁴ +(p - 3)x ³ + (2 - 3 p + q)x ² +(2 p - 3 q)x + 2 q 中不含 x ² 项和 x 项

∴ 2 - 3 p + q = 0
2 p - 3 q = 0

整理得:3 p - q = 2 ①
2 p - 3 q = 0 ②

① × 3 得:9 p - 3 q = 6 ③

③ - ② 得:7 p = 6
p = 6 / 7

代入 ① 得:
3 × 6 / 7 - q = 2
- q = 2 - 18 / 7
- q = - 4 / 7
q = 4 / 7

∴ p = 6 / 7 ,q = 4 / 7