Jawabanmu

2014-06-01T13:00:34+07:00
X² - 3x - 4 = 0

p + q = -3
p.q = -4

jadi p = -4 dan q = 1

x² - 4x + x - 4 = 0
x² + x - 4x - 4 = 0
(x² + x)(-4x -4) = 0
x (x + 1) -4 (x + 1) = 0
(x - 4)(x + 1)

x1 - 4 = 0
x1 = 4

x2 + 1 = 0
x2 = - 1

jadi
2 . x1 + 5 . x2 = ....
= 2 . 4 + 5 . (-1)
= 8 + (-5)
= 8 - 5
= 3