F.4 maths

是否打錯題目 --- 2^2 ??

2010-10-14 20:29:03 補充：
I change α and β into a and b for me to type conveniently
a + b = -(-6/2) = 3
ab = 3/2
a) a - b
= √(a-b)^2
= √(a^2 - 2ab + b^2)
= √[(a+b)^2 - 4ab]
= √[3^2 - 4(3/2)]
= √(9 - 6)
= √3

b) a^4 - b^4
= (a^2 + b^2)(a^2 - b^2)
= [(a+b)^2 - 2ab](a+b)(a-b)
= [3^2 - 2(3/2)](3)(√3)
= (6)(3√3)
= 18√3