✔ 最佳答案
兩根的和 = α + β = - (-3/1) = 3
兩根的積 = αβ = -5/1 = -5
(a) (α + 2β)(2α + β)
= 2α^2 + αβ + 4αβ + 2β^2
= 2α^2 + 2β^2 + 5αβ
= 2(α^2 + β^2) + 5αβ
= 2(α^2 + β^2 + 2αβ - 2αβ) + 5αβ
= 2[(α^2 + 2αβ + β^2 ) - 2αβ] + 5αβ
= 2[(α + β)^2 - 2αβ] + 5αβ
= 2[3^2 - 2(-5)] + 5(-5)
= 2[9 - (-10)] + (-25)
= 2(9 + 10) - 25
= 2(19) - 25
= 13
(b) (α + β)^2
= 3^2
= 9
(c) (α - α/β)(β - β/α)
= α(β - β/α) - α/β(β - β/α)
= αβ - β - α + 1
= αβ - (β + α) + 1
= -5 - 3 + 1
= -7