Question

Himpunan penyelesaian dari persamaan kuadrat 1/2x² - x - 4 = 0 adalah...

a. {4,-2}
b. {2,-4}
c. {4,2}
d. {-4,2}

(Tolong jawab pakai cara)

Answer 1

1/2x² - x - 4 = 0
a = 1/2
b = -1
c = -4
a.c = -2 = -2 + 1 = -1 (b)

1/2x² -2x + 1x - 4 = 0
(1/2x² - 2x) + (1x - 4) = 0
1/2x(x - 4) + 1(x - 4) = 0
(1/2x + 1)(x - 4) = 0
1/2x + 1 = 0 atau x - 4 = 0
1/2x = 1 atau x = 4
x = 2 atau x = 4
{4,2}