( a - 4 ) ( 4 + a ) = 4 a
=> a ( 4 + a ) - ( 4 ( 4 + a ) ) = 4 a
=> 4 a + a a - 1 6 - 4 a = 4 a
=> a a - 1 6 = 4 a
=> a a / 4 - 4 = a
=> a / 4 - 4 / a = 1
=> a - 1 6 / a = 4
=> a - ( 1 6 / a + 4 ) = 0
=> a a - ( 1 6 + 4 a ) = 0 a
=>( a - 4 ) a - 16 = 0
a = 0
( a - 4 ) ( 4 + a ) = 4 a
=> ( 0 - 4 ) ( 4 - 0 ) = 0
=> - 4 * 4 = 0
=> - 1 6 = 0
Why???
數-代數 (4) - 似方程 b
2009-09-19 2:44 am
回答 (1)
2009-09-19 3:17 am
✔ 最佳答案
較簡單的解：( a - 4 ) ( 4 + a ) = 4 a
=> a2 - 16 = 4a
=> a2 - 4a - 16 = 0
=> a = {-(-4) + √[(-4)2 - 4(1)(-16)]}/2 或 a = {-(-4) - √[(-4)2 - 4(1)(-16)]}/2
=> a = (4 + √80)/2 或 a = (4 - √80)/2
=> a = 2 + 2√5 或 a = 2 - 2√5 ..... (答案)
收錄日期: 2021-04-13 16:50:55
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https://hk.answers.yahoo.com/question/index?qid=20090918000051KK01081