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LV超3A名牌購物網
1.
α+β=3
αβ=-1
(α+β)^2-2αβ=9+2=11
α^3+β^3=(α+β)(α^2-αβ+β^2)=3(11+1)=36
2.
α+β=3
αβ=2
x^2-((1/α)+(1/β))x+(1/αβ)=0
==>x^2-(3x/2)+(1/2)=0
==>2x^2-3x+1=0
3.
D=4+4k>0
==>k>-1
4.
-2+9x+12-18-4x+3=0
==>x=1
5.
ad-bc=5
70(ad-bc)=70*5=350
6.
令y=2x^2-3x
y^2-y-2=0
==>(y-2)(y+1)=0
==>y=2或-1
2x^2-3x-2=0
==>x=-1/2或2
2x^2-3x+1=0
==>x=1/2或1
7.
D=k^2-4(k+3)>0
==>k>6或k<-2
8.
求三交點為(4,3),(-14,3),(4,-6)
三角形面積=(18*9)/2=81(平方單位)
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