十字相乘法因式分解求助中~~

👨🏻‍🏫 學術台數學

[匿名]

2011-09-28 5:21 am

分解因式x^4-x^2-20

回答 (4)

徐偉國

2011-09-28 6:20 am

✔ 最佳答案

x^4-x^2-20=(x^2+4)(x^2-5)
a^2-9ab+14b^2=(a-2b)(a-7b)
x^2+11xy+18y^2=(x+2y)(x+9y)

參考: me

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fighting gravity

2011-09-29 4:43 pm

x^4-x^2-20
=(x^2+4)(x^2-5)

a^2-9ab+14b^2
=(a-2b)(a-7b)

x^2+11xy+18y^2
=(x+2y)(x+9)

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其昌

2011-09-28 5:35 am

Answer:(x^2-5)(x^2+4),
Therefone x=-5 or 5
x=-4 or 4

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[匿名]

2011-09-28 5:29 am

x^4-x^2-20=(x^2-5)(x^2+4)
你當x^2 做平時既x咁睇就會明架啦.

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