設h(x,y)=(x^2/y)+(y^2/x),x,y皆複數

2011-12-01 7:46 am
設h(x,y)=(x^2/y)+(y^2/x),x,y皆複數

h( 1-√2i/1+i , 1+√2i/1+i )=______

回答 (2)

2011-12-01 4:44 pm
✔ 最佳答案
設h(x,y)=(x^2/y)+(y^2/x),x,y皆複數,求h((1-√2i)/(1+i),(1+√2i)/(1+i ))=___
Sol
x=(1-√2i)/(1+i),y=(1+√2i)/(1+i)
x+y=2/(1+i)=2(1-i)/2=1-i
xy=(1+2)/(1+2i-1)=3/(2i)=-3i/2
(x+y)/(xy)=(1-i)/(-3i/2)=(2-2i)/(-3i)=(2+2i)/3
(x^2/y)+(y^2/x)
=x^3/(xy)+y^3/(xy)
=(x^3+y^3)/(xy)
=[(x+y)^3-3(x+y)xy]/(xy)
=(x+y)^2*(x+y)/(xy)-3(x+y)
=(1-i)^2*(2+2i)/3-3(1-i)
=(-2i)(2+2i)/3-3+3i
=(4-4i)/3-3+3i
=-5/3+5i/3


2011-12-01 4:50 pm
先算x+y=2/1+i=1-i
xy=3/2i=-3i/2
乘法公式求x^2+y^2=(1-i)^2-2*(-3i/2)=i
乘法公式求x^3+y^3=(1-i)*(i-(-3i/2))=5i/2+5/2
通分h(x,y)=(x^3+y^3)/xy=(5i/2+5/2)/(-3i/2)=5/3-5/3i=5/3+5i/3

方向應該是沒錯的,如果心算錯誤,請自己算!


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