[解題] 高中數學 複數極式
1.年級:高一
2.科目:數學
3.章節:複數極式
4.題目:X^7-1=0有七個根,1,w,w^2,w^3,w^4,w^5,w^6。
1 1 1 1 1 1
--- + ----- + ----- + ----- + ----- + ----- = ?
1-w 1-w^2 1-w^3 1-w^4 1-w^5 1-w^6
5.想法:因為1,w,w^2,w^3,w^4,w^5,w^6為根,可寫成
X^7-1=(X-1)(X-w)(X-w^2)(X-w^3)(X-w^4)(X-w^5)(X-w^6)
=(X-1)(X^6+X^5+X^4+X^3+X^2+X+1)
故(X-w)(X-w^2)(X-w^3)(X-w^4)(X-w^5)(X-w^6)=X^6+X^5+X^4+X^3+X^2+X+1
X=1代入,可得(1-w)(1-w^2)(1-w^3)(1-w^4)(1-w^5)(1-w^6)=7
然後將所求通分,下面等於7,但是上面一長串,應該不可能乘開吧..
--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 118.171.101.67
推
11/15 22:34, , 1F
11/15 22:34, 1F
→
11/15 22:34, , 2F
11/15 22:34, 2F
推
11/15 22:39, , 3F
11/15 22:39, 3F
→
11/15 22:40, , 4F
11/15 22:40, 4F
→
11/15 22:45, , 5F
11/15 22:45, 5F
推
11/16 10:50, , 6F
11/16 10:50, 6F
推
11/16 15:21, , 7F
11/16 15:21, 7F
→
11/16 15:21, , 8F
11/16 15:21, 8F