標題:

maths--funtions

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發問:

http://i983.photobucket.com/albums/ae311/zachariah_thomas/abc/21-25.jpg plz help the above Qs,thz!!!

最佳解答:

21.(a) f(x) = x^3 + ax + b f(x) = q(x)(x-4) + 32 put x = 4, we have 64 + 4a + b = 32. Also, f(x) = r(x)(x+2) - 10 put x = -2, we have -8 - 2a + b = -10 Upon solving above two equations, we have a = -5, b = -12 Therefore, f(x) = x^3 - 5x - 12 (b) I think the question is wrong, since f(2) =/= 0. But f(3) = 27 - 15 - 12 = 0. So, (x-3) is a factor... 22. x^3 - 2x + a = q(x)(x-1) + C where C is the remainder, Put x = 1. a - 1 = C 2x^3 + x - a = r(x)(2x+1) + C Put x = -1/2 -3/4 - a = C Therefore, a - 1 = -3/4 - a 2a = 1/4 a = 1/8

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