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標題:

Form 2 Mathematics

發問:

1.which of the following is/are true? (I) (a-b)(a-b) = (b-a)(b-a) (II) (-a-b)(-a-b) = (a+b)(a+b) (III) (-a+b)(-a+b) = (a-b)(a-b) A. (II) only B. (I) and (II) only C. (II) and (III) D. all of the above

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• 我想問韓劇旋轉木馬_7
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答案係D 我唔記得中二學左take out common factor未(記憶中好似有) l (a-b) (a-b) = (b-a) (b-a) (a-b) (a-b) = -1(-b+a) x (-1) (-b+a) (a-b) (a-b) = (a-b) (a-b) 成立 因為-1 x -1 = 1(負負得正) ll (-a-b) (-a-b) = (a+b) (a+b) -1(a+b) x (-1) (a+b) = (a+b) (a+b) (a+b) (a+b) = (a+b) (a+b) 成立 lll (-a+b) (-a+b) = (a-b) (a-b) -1(a-b) x (-1) (a-b) = (a-b) (a-b) (a-b) (a-b) = (a-b) (a-b) 成立 因為 l ll lll 都成立 ,所以答案係D

其他解答:

if a=3,b=2 (I)(3-2)(3-2)=(2-3)(2-3).........false (II)(-3-2)(-3-2)=(3+2)(3+2).......true (III)(-3+2)(-3+2)=(3-2)(3-2).........true therefore ,answer is C|||||d (a-b)(a-b)=(b-a)(b-a) a*a+b*b-2ab=a*a+b*b-2ab|||||C is true