Akar persamaan x3 + 2x -15x + k = 0 mempunyai sepasang akar saling berlawanan. Tentukan nilai k

POLINOM

pangkat tiga
ada tiga akar akarnya
misal x1 berlawanan dgn x2
x1 + x2 = 0

dari persamaan
x1 + x2 + x3 = -2/1 = -2
0 + x3 = -2
x3 = -2

x1.x2 + x1.x3 + x2.x3 = -15/1 = -15
x1.x2 + x3(x1 + x2) = -15
x1.x2 + x3.(0) = -15
x1.x2 + 0 = -15
x1.x2 = -15


x1.x2.x3 = k/1
(x1.x2).x3 = k
(-15).(-2) = k
30 = k
k = 30

jd nilai k = 30