已知2x^2-5x+1=-1及xy^2=3。伊華說8x^3-20x^2y^2+4xy^2的值是12。你是否同意？試解釋你的答案。?
回答 (1)
2018-06-17 5:22 pm
✔ 最佳答案
Sol2x^2－5x+1=－1
2x^2－5x+2=0
(2x－1)(x－2)=0
x=1/2 or x=2
(1) x=1/2
xy^2=3
y^2=6
8x^3－20x^2y^2+4xy^2
=8*(1/2)^3－20*(1/2)^2*6+4*(1/2)*6
=8*(1/8)－20*(1/4)*6+4*(1/2)*6
=1－30+12
=－17
(2) x=2
xy^2=3
y^2=3/2
8x^3－20x^2y^2+4xy^2
=8*(2)^3－20*2^2*(3/2)+4*2*(3/2)
=8*8－20*4*(3/2)+4*2*(3/2)
=64－120+12
=－46
不同意
收錄日期: 2021-04-28 22:14:51
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20180616142511AA5DLUQ