F.3數學問題

🎓 學業台小學及中學教育

用戶199746

2007-11-28 6:11 am

1. x^3+64
=(x+4)(x^2+4x+16)
Hence factorize x^3-7x+36

2. x^3-27
=(x-3)(x^2+3x+9)
Hence factorize x^3+4x^2-11x-30

Please give steps also! Thank you!

更新1:

sorry! typed the wrong thing~ 1. x^3+64 =(x+4)(x^2-4x+16)

回答 (2)

STEVIE-G™

2007-11-28 6:34 am

✔ 最佳答案

圖片參考：http://hk.geocities.com/stevieg_1023/x3.gif

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蠍子

2007-11-28 6:22 am

1. x^3+64
=x^3+4^3
=(x+4)(x^2-4x+4^2)
=(x+4)(x^2-4x+16)

因為
a^3+b^3 = (a+b)(a^2-ab+b^2)
a^3-b^3 = (a-b)(a^2+ab+b^2)

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