If x+y = a and xy = b, express the following in terms of a and b.
1.) x^4+y^4
thz`
都幾易既數 ..
2008-03-15 1:32 am
回答 (2)
2008-03-15 1:47 am
✔ 最佳答案
(x+y)^4=x^4+4x^3y+6x^2y^2+4xy^3+y^4
=x^4+y^4+2xy(2x^2+3xy+2y^2)
=x^4+y^4+2xy[2(x+y)^2-xy]
x^4+y^4
=(x+y)^4-2xy[2(x+y)^2-xy]
=a^4-2b[2a^2-b]
=a^4-4a^2b+2b^2
2008-03-15 2:26 am
x^4+y^4= 4
x^4+y^4= 4
x^4+y^4= 4
x^4+y^4= 4
x^4+y^4= 4
x^4+y^4= 4
x^4+y^4= 4
x^4+y^4= 4
x^4+y^4= 4
收錄日期: 2021-04-25 16:58:57
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