bu_zhidao
幼苗
共回答了22个问题采纳率:95.5% 举报
当z是实数时:虚数部分等于零
a^2 - 5a - 6 = 0
(a + 1)(a - 6) = 0
(当a = - 1,z = 7,当a = 6,z = 0)
a = - 1 OR a = 6
当z是虚数时:虚数部分不等于零
(a² - 5a - 6) ≠ 0
a ≠ - 1 OR a ≠ 6
当z是纯虚数时:实数部分等于零
(a² - 7a + 6)/(a² + 1) = 0
a² - 7a + 6 = 0
(a - 1)(a - 6) = 0
(当a = 1,z = - 10i,当a = 6,z = 0,0是实数,不符合)
所以a = 1
1年前
7