2(x+7)+3(x-5)=(x-2)+9
證明條數係恆等數
小六數學題
2009-09-18 7:22 am
回答 (2)
2009-09-18 7:36 am
✔ 最佳答案
左邊： 2(x+7)+3(x-5)＝２x+14+3x-15
=5x-1
右邊：(x-2)+9
＝x+7
假設：5x-1=x+7
5x-x=7+1
4x=8
x=2
將x=2代入左邊數式
5x-1＝５x2-1
=10-1
=9
將x=2代入右邊數式
x+7＝２＋７
＝９
所以：右邊數式＝左邊數式
即：2(x+7)+3(x-5)=(x-2)+9 是恆等數式
2009-09-18 3:03 pm
2(x + 7) + 3(x - 5)
= (2)(x) + (2)(7) + (3)(x) - 3(5)
= 2x + 14 + 3x - 15
= 5x - 1
= 5x - 10 + 9
= 5x - (5)(2) + 9
= 5(x - 2) + 9
所以左邊恒等右邊
= (2)(x) + (2)(7) + (3)(x) - 3(5)
= 2x + 14 + 3x - 15
= 5x - 1
= 5x - 10 + 9
= 5x - (5)(2) + 9
= 5(x - 2) + 9
所以左邊恒等右邊
收錄日期: 2021-04-13 16:50:52
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