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f.4 maths *e
發問:
P.95 It is given that 2x^3+9x^2-8x-k is divisible by x+5 a)Find the value of k. b)Hence,factorize 2x^3+9x^2-8x-k completely.
最佳解答:
(a) Let f(x) = 2x^3+9x^2-8x-k f(-5) = 0 2(-5)^3 + 9(-5)^2 - 8(-5) - k = 0 -250+225+40-k = 0 k = 15 (b) By long division, 2x^3+9x^2-8x-15 = (x+5)(2x^2-x-3) = (x+5)(2x-3)(x+1)
其他解答:
a, Let x be( -5) 2x^3+9x^2-8x-k=0 -2*125+9*25+40-k=0 k=15 b. 2x^3+9x^2-8x-k =2x^3+9x^2-8x-15 =(x+5)(2x^2-x-3) =(x+5)(x+1)(2x-3)4E350C6F8B48ECA2
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