1.(x+3y)二次方-6(x+3y)(x-y)+9(x-y)二次方
2.4x二次方-4x-15
Please write the step clearly.Thx
maths
2010-10-24 2:40 am
回答 (2)
2010-10-24 3:03 am
✔ 最佳答案
------------------------------------------------------------------------------------圖片參考：http://img36.imageshack.us/img36/7528/quadratic.png
2010-10-23 19:06:27 補充：
http://img36.imageshack.us/img36/7528/quadratic.png
2010-10-24 3:12 am
1.
設 u = x + 3y 及 v = x - y
(x + 3y)² - 6(x + 3y)(x - y) + 9(x - y)²
= u² - 6uv + 9v²
= u² - 2u(3v) + (3v)²
= (u - 3v)²
= [(x + 3y) - 3(x - y)]²
= (x + 3y - 3x + 3y)²
= (6y - 2x)²
= 4(3y - x)²
(或 4(x - 3y)²)
2.
4x² - 4x - 15
= 4x² - 10x + 6x - 15
= (4x² - 10x) + (6x - 15)
= 2x(2x - 5) + 3(2x - 5)
= (2x + 3)(2x - 5)
設 u = x + 3y 及 v = x - y
(x + 3y)² - 6(x + 3y)(x - y) + 9(x - y)²
= u² - 6uv + 9v²
= u² - 2u(3v) + (3v)²
= (u - 3v)²
= [(x + 3y) - 3(x - y)]²
= (x + 3y - 3x + 3y)²
= (6y - 2x)²
= 4(3y - x)²
(或 4(x - 3y)²)
2.
4x² - 4x - 15
= 4x² - 10x + 6x - 15
= (4x² - 10x) + (6x - 15)
= 2x(2x - 5) + 3(2x - 5)
= (2x + 3)(2x - 5)
參考: 土扁
收錄日期: 2021-04-13 17:36:11
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