Challenging Maths

As follows:

圖片參考：http://i117.photobucket.com/albums/o61/billy_hywung/Sep07/Angel2.jpg

Since x = ( 3 + 5√(-1) ) / 2 = ( 3 + 5i ) /2

Then,

2x^3 + 2x^2 - 7x + 72

= 2 [ ( 3 + 5i ) /2 ] ^3 + 2 [ ( 3 + 5i ) /2 ]^2 - 7 [ ( 3 + 5i ) /2 ] + 72

= 2 ( -99/4 + 5i/4 ) + 2 ( -4 + 15i/2 ) - 7 [ ( 3 + 5i ) / 2 ] + 72

= -99/2 + 5i/2 - 8 - 15i - 21/2 - 35i/2 + 72

= -99/2 - 8 - 21/2 +72 + 5i/2 - 15i - 35i/2

= 4 - 30i

2007-09-14 14:14:16 補充：
上面果一位係[（3+5i )/2 ] ^ 2 既中間1/4 ( -16 + 30i ) 果度之後應該是 1/2 ( -8 +15i )而唔係 1/2 ( -4 +15i )