✔ 最佳答案
a + b = 2 [sum of roots]
ab = -6 [product of roots]
(a-b)^2 = a^2 - 2ab + b^2
=(a^2-2ab+b^2)+4ab
=(a-b)^2 + 4ab
=2^2 + 4*-6
=-20
2007-04-21 18:49:36 補充:
some mistake in the middleThe corrected one:(a-b)^2 = a^2 - 2ab + b^2=(a^2+2ab+b^2)+4ab=(a+b)^2 + 4ab=2^2 + 4*-6=-20However, the answer is the same