美夢成真教甄討論區

請參考附件

計算第 1 題
2(a^2 + b^2) ≧ (a + b)^2 > a + b (∵ a + b ≧ 3)

|a - 2b^2| + |b - 2a^2|
≧ |(a + b) - 2(a^2 + b^2)|
= 2(a^2 + b^2) - (a + b)
≧ (a + b)^2 - (a +b)
= (a + b)(a + b - 1)
≧ 3 * 2
= 6