Jika x1 dan x2 adalah akar-akar persamaan kuadrat x²+2x-4=0, maka x1³+x2³=

jika : (x₁+x₂)³ = x₁³+3 (x₁+x₂) x₁.x₂ + x₂³
                      = x₁³+ x₂³ +3 (x₁+x₂) x₁.x₂
 
         x₁³+ x₂³ =  (x₁+x₂)³ - 3 (x₁+x₂) x₁.x₂   

x²+2x-4=0

x₁+x₂ = -2
x₁.x₂  = -4

x₁³+ x₂³ =  (x₁+x₂)³ - 3 (x₁+x₂) x₁.x₂   
             = (-2)³ - 3 (-2)(-4)
             = -8 - 24
            = -32

x1+x2=-b/a
= -2/1
=-2
x1.x2=c/a
=4/1
=4
dit x1^3+x^3 =?
Jwb

x1^3+x2^3=(x1+x2)^3 -3(x1+x2)(x1.x2)
=(-2)^3 -3(2)(4)
=-8-24
=-32