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標題:
一條簡單數學問題
發問:
此文章來自奇摩知識+如有不便請留言告知
(a) Factorize x^2 – 2x – 24. (b) Let a^2 + 4a = x. Using the result in part (a), factorize (a^2 + 4a)^2 – 2(a^2 + 4a) – 24.
最佳解答:
(a) Factorize x2 - 2x - 24 Using cross method, x -6 x +4 +4x - 6x = -2x x2 - 2x - 24 = ( x - 6 )( x + 4 ) (b)Let a2 + 4a = x ( a2 + 4a )2 - 2( a2 + 4a ) - 24 = x2 - 2x - 24 = ( x - 6 )( x + 4 ) ( by part a ) = ( a2 + 4a - 6 )( a2 + 4a + 4 )
其他解答:
Ans for b should be: =( a^2 + 4a - 6 )( a^2 + 4a + 4 ) =( a^2 + 4a - 6 )(a +2)^ 2
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