Question

宣(*'へ'*)

算起來答案是－3可是正解是1＼2

(4)設1-i是x²+ax+3+i=0的一根,則a=?

Answer 1

qn

代入
(1-i)² + a(1-i) + 3+i = 0
(1-2i-1) + a(1-i) + 3+i = 0
(1-i) a + (3-i) = 0
a = (-3+i) / (1-i)
= (-3+i)(1+i) / (1²-i²)
= (-4-2i)/2
= -2-i