47. When a polynomial f(x) is divided by x-5, the remainder is 9. When f(x) is divided by x+2, the remainder is -5. Find the remainder when f(x) is divided by (x-5)(x+2). (model ans: 2x-1)
46. The remainder when a polynomial f(x) is divided by (x-2)(x+3) is ax+b. When f(x) is divided by x-2, the remainder is 5. x+3 is a factor of f(x). Find the values of a and b. (model ans: a=1, b=3)
45. It is given that x(2次方) + x - 6 is a factor of f(x) =x(3次方)+ax(2次方)-14x+b .
(a) Find the values of a and b. (model ans:a=-7, b=48)
(b) Factorize f(x). (model ans: (x-2)(x+3)(x-8) )
这题 重点 想问的是 (a) 部分, 我 是 用 非传统非正规(书中未教的法子)方法 侥幸 算出, 即 长除法。 因为 一般都是 给 linear factor, 但这次是给 quadratic factor: x(2次方)+x -6。 如何在 x(2次方)+x -6 身上 使用 factor theorem? 因为根据 书中所说,用 factor theorem 才是 正规方法。
43.(b) Factorize the following polynomials. 3x(3次方)+4x(2次方)-10x+4
(model ans: (3x-2)(x(2次方)+2x-2) )
这题 和上一题有点像, 不过方向好像是反过来的。如果我不先去求得 factor (3x-2), 怎 么先 从 3x(3次方) 和 4 中 抽出/ 先求出 (x(2次方)+2x-2)???
41. Let f(x) be a polynomial. When f(x) is divided by x+2, the quotient is 2x(2次方)-13x+18. It is given that x-5 is a factor of f(x). (a) Find f(x). (b)...(唔重要,难系难在(a)) (model ans: 2x(3次方)-9x(2次方)-8x+15)
这题无讲明 有无 remainder,够 怪鸡, 而 之后计算证明有 remainder, 但我又系用小小智慧 用非正规 法子 预计出 答案,正规法子系点? 关键系条式无太知点写。